Method for replenishing development replenisher in automatic developing machine for photosensitive lithographic printing plate precursor and automatic photosensitive lithographic printing plate precursor developing machine

ABSTRACT

A development replenisher replenishment method in an automatic developing machine for a photosensitive lithographic printing plate precursor, the method comprising: developing a plurality of sheets of exposed photosensitive lithographic printing plate precursors with a developer containing an electrolyte while replenishing a development replenisher to keep a developer activity constant, wherein an electric conductivity of the developer is measured every constant period; a development replenisher is replenished every constant time as a time lapse replenisher in an amount based on a set value of a time lapse replenishment rate; a development replenisher is replenished every processing of a constant area of a photosensitive lithographic printing plate precursor(s) as a processing replenisher in an amount based on a set value of a processing replenishment rate; a calculated value of an electric conductivity is calculated from an amount of the time lapse replenisher and an amount of the processing replenisher; and when a set value of a replenishment system indicates an electric conductivity system, the set value of the time lapse replenishment rate and the set value of the processing replenishment rate are increased or decreased according to a result of a comparison of the calculated value of the electric conductivity with the measured value of the electric conductivity of the developer, or when a set value of a replenishment system does not indicate an electric conductivity system, the set value of the time lapse replenishment rate and the set value of the processing replenishment rate are not increased or decreased.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to au automatic developing method in an automatic developing machine and an automatic developing machine therefor and more particularly to a technique for minimizing fluctuation in developer sensitivity due to change in development processing conditions.

2. Description of the Related Art

In order to control the sensitivity of developer in the automatic developing machine for a photosensitive lithographic printing plate precursor, there is ordinarily employed a system of replenishing a development replenisher according to time lapse and processing amount to a developer (hereinafter referred to as an “area and time lapse-based replenishment system”), where the development replenisher is replenished with the passage of time to a developing tank storing the developer and at the same time, the development replenisher is replenished in an amount according to a value determined by measuring a plate area of the lithographic printing plate precursor processed.

However, this area and time lapse-based replenishment system is disadvantageous in that the development portion of the automatic developing machine requires a high precision device for measuring the area of lithographic printing plate, causing the complication of configuration and the cost rise. This system is also disadvantageous in that it is difficult to judge to see which the lithographic printing plate precursor is photosensitive only on one side thereof or on both sides thereof and judge the kind of the printing plate precursor (e.g., printing plate precursors having different spreads of photosensitive layer composition). This raises a problem that when the required replenishment rate of developer replenisher changes with the change of the area and kind of lithographic printing plate precursor used and which the lithographic printing plate precursor is photosensitive only on one side thereof or on both sides thereof, it is made difficult to make proper replenishment of developer replenisher.

Under these circumstances, as the method of replenishing a development replenisher in the automatic developing machine for a photosensitive lithographic printing plate precursor, a system of replenishing a development replenisher to a developer (hereinafter referred to as an “electric conductivity-based replenishment system”) is known as described, for example, in Japanese Patent No. 2516022 (corresponding to JP-A-64-21451), where electric conductivity of the developer is measured, the measured value is compared with an electric conductivity value for providing an optimum sensitivity (hereinafter referred to an “adequate electric conductivity value”) that is experimentally determined previously, and the development replenisher is replenished when the measured value falls below the adequate electric conductivity value. The electric conductivity-based replenishment system ensures replenishment of an adequate amount of development replenisher to adequately maintain the sensitivity of developer, even with the change of the area and kind of lithographic printing plate precursor used and which the lithographic printing plate precursor is photosensitive only on one side thereof or on both sides thereof.

However, an experimental fact is generally known that a developer which has been fatigued only with carbon dioxide gas with time and a developer which has been fatigued only with plate processing differ from each other in adequate electric conductivity (silicate-based processing agent/fatigue with time (fatigue with carbon dioxide gas) at the time of replenishment restoration: 65 mS/cm; fatigue with processing at the time of replenishment restoration: 55 mS/cm; nonsilicate-based processing agent/fatigue with time at the time of replenishment restoration: 56 mS/cm; fatigue with processing at the time of replenishment restoration: 39 mS/cm). Therefore, in the aforementioned electric conductivity-based replenishment system, when the frequency of processing, e.g., amount processed per day differs from expected value, the ratio of actual time lapse replenishment rate to processing replenishment rate, too, differs from expected value. This causes the change of the adequate electric conductivity of the entire developer in the developing tank calculated from each adequate electric conductivity and hence the occurrence of some deviation from predetermined adequate electric conductivity, making it impossible to keep the sensitivity of developer adequate to disadvantage.

On the other hand, JP-A-9-96910 and JP-A-2004-219452, which is an improvement in JP-A-9-96910, each propose an automatic developing machine which measures the time interval of replenishment, determines the time lapse replenishment rate required within the time interval, regards the value obtained by subtracting the time lapse replenishment rate from the replenishment rate per one processing as processing replenishment rate to determine processing replenishment rate and time lapse replenishment rate and uses the electric conductivity calculated from the ratio of processing replenishment rate to time lapse replenishment rate thus determined to control the electric conductivity of developer. In accordance with this method, even with the change of the area and kind of the lithographic printing plate precursor to be processed and which the lithographic printing plate precursor is photosensitive only on one side thereof or on both sides thereof, the adequate electric conductivity of developer can be determined by estimating the ratio of processing replenishment rate to time lapse replenishment rate. In this method, however, the difference of required time lapse replenishment rate caused by the difference of developer fatigue with carbon dioxide gas (e.g., difference of developer temperature, presence or absence of liquid circulation) between during the operation of the automatic developing machine and during the suspension of the operation of the automatic developing machine cannot be detected, making it impossible to determine accurate ratio of processing replenishment rate to time lapse replenishment rate from time interval of replenishment across the suspension of the operation of the automatic developing machine. It is thus likely that some erroneous value of electric conductivity can be a reference value.

Under these circumstances, JP-A-2004-212681 proposes a method of calculating a reference value of electric conductivity using different calculation formulae from at the time of starting the automatic developing machine which is replenished with a required replenisher at the time of suspension thereof to during the operation of the automatic developing machine.

SUMMARY OF THE INVENTION

However, the aforementioned method which comprises controlling the electric conductivity of developer according to the electric conductivity determined from the ratio of processing replenishment rate to time lapse replenishment rate calculated from the time interval of replenishment is disadvantageous in that when the conditions of fatigue with time vary, accurate ratio of processing replenishment rate to time lapse replenishment rate cannot be determined. Referring further to the variation of conditions of fatigue with time, there are some cases where the concentration of atmospheric carbon dioxide gas varies or the wind velocity of atmosphere varies. It is known that the former case of variation depends on the number of workers in the room where the automatic developing machine is installed while the latter case of variation depends on the position of the nozzle of air conditioner or the air flow. In other words, in accordance with the aforementioned replenishment system, there occurs some difference between the time lapse replenishment rate at a unit time interval which has been previously determined experimentally and the time lapse replenishment rate at an actual unit time interval depending on the increase or decrease of the number of workers in the chamber or the conditions of the air conditioner, making it impossible to determine accurate time lapse replenishment rate from the time interval of replenishment. It is thus likely that erroneous target value of electric conductivity can be calculated.

It is also known that an electrode type electric conductivity sensor can be stained on the surface of the electrode to cause erroneous operation depending on what kind of developer or plate material is used. It is likely that when the value of electric conductivity measured by the electric conductivity sensor becomes abnormal due to stain on the electrode, the aforementioned related art electric conductivity-based replenishment system cannot control the developer activity.

It is thus an aim of the invention to provide a development replenisher replenishing method for automatic developing machine for photosensitive lithographic printing plate precursor capable of minimizing the fluctuation of developer sensitivity against the change of development conditions despite the simple and inexpensive configuration of the development portion of the automatic developing machine and an automatic photosensitive lithographic printing plate precursor developing machine.

The aforementioned aims of the invention are accomplished by the following constitutions (1) to (4).

(1) A development replenisher replenishment method in an automatic developing machine for a photosensitive lithographic printing plate precursor, the method comprising:

developing a plurality of sheets of exposed photosensitive lithographic printing plate precursors with a developer containing an electrolyte while replenishing a development replenisher to keep a developer activity constant,

wherein an electric conductivity of the developer is measured every constant period;

a development replenisher is replenished every constant time as a time lapse replenisher in an amount based on a set value of a time lapse replenishment rate;

a development replenisher is replenished every processing of a constant area of a photosensitive lithographic printing plate precursor(s) as a processing replenisher in an amount based on a set value of a processing replenishment rate;

a calculated value of an electric conductivity is calculated from an amount of the time lapse replenisher and an amount of the processing replenisher; and

when a set value of a replenishment system indicates an electric conductivity system, the set value of the time lapse replenishment rate and the set value of the processing replenishment rate are increased or decreased according to a result of a comparison of the calculated value of the electric conductivity with the measured value of the electric conductivity of the developer, or

when a set value of a replenishment system does not indicate an electric conductivity system, the set value of the time lapse replenishment rate and the set value of the processing replenishment rate are not increased or decreased.

(2) A development replenisher replenishment method in an automatic developing machine for a photosensitive lithographic printing plate precursor, the method comprising:

developing a plurality of sheets of exposed photosensitive lithographic printing plate precursors with a developer containing an electrolyte while replenishing a development replenisher to keep a developer activity constant,

wherein an electric conductivity of the developer is measured every constant period,

a set value of a time lapse replenishment rate is integrated to an integrated value of the time lapse replenishment rate every constant time;

a set value of a processing replenishment rate is integrated to an integrated value of the processing replenishment rate every processing of a constant area of a photosensitive lithographic printing plate precursor(s);

a percent replenisher replacement which is a ratio of a developer replenishment to a developer in a developing tank is calculated;

a percent time lapse replenishment which is a ratio of a time lapse replenisher to a developer in a developing tank is calculated; and

thereafter, when a sum of the integrated value of the time lapse replenishment rate and the integrated value of the processing replenishment rate exceeds a value of the lowest replenishment amount, and

a set value of a replenishment system indicates an electric conductivity system, steps (A-1), (A-2), (A-3), (A-4), (A-5) and (A-6) are executed, or a set value of a replenishment system does not indicate an electric conductivity system, steps (B-1) and (B-2) are executed:

(A-1) a time elapsed between the last time of replenishment and a present time is measured, and a first calculated value of an electric conductivity is calculated from the elapsed time and the percent replenisher replacement;

(A-2) the set value of the time lapse replenishment rate and the set value of the processing replenishment rate are changed according to a result of a comparison of the first calculated value of the electric conductivity with the measured value of the electric conductivity of the developer;

(A-3) a second calculated value of an electric conductivity is calculated by utilizing the percent replenisher replacement and the percent time replenishment;

(A-4) the set value of the time lapse replenishment rate and the set value of the processing replenishment rate are changed according to a result of a comparison of the second calculated value of the electric conductivity with the measured value of the electric conductivity of the developer;

(A-5) a developer in a developing tank is replenished with a replenisher in an amount corresponding to a sum of the integrated value of the time lapse replenishment rate and the integrated value of the processing replenishment rate; and

(A-6) the integrated value of the time lapse replenishment rate and the integrated value of the processing replenishment rate are initialized,

(B-1) a developer in a developing tank is replenished with a replenisher in an amount corresponding to a sum of the integrated value of the time lapse replenishment rate and the integrated value of the processing replenishment rate; and

(B-2) the integrated value of the time lapse replenishment rate and the integrated value of the processing replenishment rate are initialized.

(3) The development replenisher replenishment method in an automatic developing machine for a photosensitive lithographic printing plate precursor as described in (2) above,

wherein a value of the electric conductivity at which the developer activity falls within a proper range is calculated as a target value of the electric conductivity; and

when a set value of a replenishment system indicates an electric conductivity system shortly after a starting of an operation of the automatic developing machine, steps (C-1), (C-2), (C-3) and (C-4) are executed, or when a set value of a replenishment system does not indicate an electric conductivity system, a developer is replenished with a developer replenisher according to a period of time during which the operation of the automatic developing machine has been suspended:

(C-1) an electric conductivity of the developer is measured every constant period;

(C-2) when the measured value of the electric conductivity of the developer is lower than the target value of the electric conductivity, the developer is replenished with a development replenisher in a predetermined amount;

(C-3) the target value of the electric conductivity is renewed with the replenishment; and

(C-4) the steps (C-1), (C-2) and (C-3) are repeated until the electric conductivity of the developer exceeds the target value of the electric conductivity.

(4) An automatic photosensitive lithographic printing plate precursor developing machine for developing a plurality of sheets of exposed photosensitive lithographic printing plate precursors with a developer containing an electrolyte while replenishing a development replenisher to keep the developer activity constant, the machine comprising:

a developing unit that develops the photosensitive lithographic printing plate precursors with a developer;

an electric conductivity measuring unit that measures an electric conductivity of a developer; and

a developer replenishment unit that replenishes a developer with a development replenisher,

wherein the developer is replenished with the development replenisher according to a development replenisher replenishment method as described in (2) or (3) above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configurational view of a first embodiment of the automatic developing machine implementing the development controlling method of the invention;

FIG. 2 is a flow chart illustrating a first controlling by a controlling device in the development controlling method of the invention;

FIG. 3 is a flow chart (part 1) illustrating a second controlling by a controlling device in the development controlling method of the invention;

FIG. 4 is a flow chart (part 2) illustrating a second controlling by a controlling device in the development controlling method of the invention;

FIG. 5 is a flow chart (part 1) illustrating a third controlling by a controlling device in the development controlling method of the invention;

FIG. 6 is a flow chart (part 2) illustrating a third controlling by a controlling device in the development controlling method of the invention;

FIG. 7 is a flow chart (part 3) illustrating a third controlling by a controlling device in the development controlling method of the invention; and

FIG. 8 is a configurational view of a second embodiment of the automatic developing machine implementing the development controlling method of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The term “development replenisher” as used in the present invention means a processing solution replenished so as to keep constant the development performance. The replenisher ordinarily includes that obtained by diluting a replenisher stock solution with a diluent (e.g., water) and the replenisher stock solution itself using without diluting it. In the present invention, the “development replenisher” means a processing solution prepared by diluting a replenisher stock solution with a diluent. The replenishment method includes a method where a replenisher prepared by previously diluting a replenisher stock solution may be replenished to a developer and a method where a replenisher stock solution and a diluent may be separately replenished directly to a developer.

Also, in the present invention, an electric conductivity sensor for measuring an electric conductivity value of developer means a known device, for example, an alternating current electric conductivity meter, an alternating current bridge meter and other electric conductivity meters. In addition, optimal conditions of measured current value, oscillating frequency and the like of the measuring device vary depending on the composition or the like of the developer. However, in view of the device and for preventing electrolysis of the water-soluble developer, the current value is preferably low to a certain extent, specifically, from several hundreds of mA to several μA. Furthermore, in view of relationship with an electrostatic capacity component in the developer, the frequency is preferably from several hundreds of Hz to several hundreds of kHz.

The electric conductivity value of developer containing an electrolyte depends on temperature of the aqueous solution, and the value decreases as the liquid temperature rises. Accordingly, the electric conductivity is more preferably measured by a measuring device equipped with a temperature sensor and a temperature compensating circuit. Also, the temperature may be compensated by converting an actually measured liquid resistance value and liquid temperature into an electric conductivity value at a predetermined temperature in a controlling device for controlling the replenishment. A sensor of the alternating current electric conductivity meter, alternating current bridge meter or other electric conductivity meter may be disposed at any position as long as it is a place where the sensor can be immersed in the developer at the measurement and can measure the alternating current electric conductivity value of the developer. For example, the sensor is preferably disposed in a developer circulation system of an automatic developing machine, particularly, in a developing tank or circulation pipe. As for a detecting unit, a known measuring cell using as an electrode, platinum, stainless steel or the like can be employed.

Preferred embodiments of the method for automatic development of photosensitive lithographic printing plate precursor according to the invention and the automatic developing machine therefor will be described hereinafter.

Firstly, the alkali development processing solution to be used in the automatic developing machine of the invention will be described. The alkali development processing solution of the invention can be used as a developer (hereinafter referred to as “development starting solution”) to be charged at the beginning of development or a development replenisher. The development starting solution and the development replenisher will be totally referred to as “developer” unless otherwise specified.

The developer of the invention is essentially composed of alkaline aqueous solution and can be appropriately selected from conventionally known aqueous alkali solutions.

Examples of the aqueous alkali solution include a developer comprising an alkali silicate and a base and a developer comprising a nonreducing sugar and a base. In particular, those having a pH of 12.5 to 14.0 are preferred.

The alkali silicate is that showing alkalinity when dissolved in water, and examples thereof include an alkali metal silicate, for example, sodium silicate, potassium silicate or lithium silicate, and ammonium silicate.

The alkali silicates may be used individually or in combination of two or more thereof.

The developing property of the aqueous alkali solution can be easily adjusted by controlling a mixing ratio of silicon oxide SiO₂ and alkali oxide M₂O (M represents an alkali metal or an ammonium group) that are the silicate components, or controlling a concentration.

Among the above-described aqueous alkali solutions, those where a mixing ratio of silicon oxide SiO₂ to alkali oxide M₂O (SiO₂/M₂O by mol) is from 0.5 to 3.0 are preferred. When the mixing ratio silicon oxide SiO₂ to alkali oxide M₂O (SiO₂/M₂O by mol) falls within this range, the general-purpose aluminum plate to be used as support for lithographic printing plate precursor does not need to be etched, giving good developing properties. Those where the mixing ratio SiO₂/M₂O (molar ratio) is from 1.0 to 2.0 are more preferred.

The concentration of the alkali silicate in the developer is preferably from 1 to 10% by mass, more preferably from 3 to 8% by mass, and most preferably from 4 to 7% by mass, based on the weight of the aqueous alkali solution from the standpoint of developing properties, processing properties and convenience of waste liquid disposal. (In this specification, % by mass is equal to % by weight.)

In the developer comprising a nonreducing sugar and a base, the nonreducing sugar means a saccharide having no reducing property due to absence of a free aldehyde group or a free ketone group. The nonreducing sugar is classified into a trehalose-type oligosaccharide where reducing groups are bonded to each other; a glycoside where a reducing group of saccharide is bonded to a non-saccharide; and a sugar alcohol produced by reducing a saccharide through hydrogenation. In the present invention, any of the nonreducing sugars can be preferably used.

Examples of the trehalose-type oligosaccharide include saccharose and trehalose. Examples of the glycoside include an alkyl glycoside, a phenol glycoside and a mustard oil glycoside.

Examples of the sugar alcohol include D,L-arabitol, ribitol, xylitol, D,L-sorbitol, D,L-mannitol, D,L-iditol, D,L-talitol, dulcitol and allodulcitol. Other preferable examples include maltitol obtained by hydrogenation of disaccharide and a reduced product (reduced starch syrup) obtained by hydrogenation of oligosaccharide.

Among the nonreducing sugars, preferred are a sugar alcohol and saccharose, and more preferred are D-sorbitol, saccharose and reduced starch syrup because of their buffering activity in an appropriate pH region. The nonreducing sugars may be used individually or in combination of two or more thereof. A content of the nonreducing sugar in the developer is preferably from 0.1 to 30% by mass, more preferably from 1 to 20% by mass.

In combination with the alkali silicate or nonreducing sugar, an alkali agent appropriately selected from conventionally known alkali agents can be used as the base.

Examples of the alkali agent include inorganic alkali agents such as sodium hydroxide, potassium hydroxide, lithium hydroxide, trisodium phosphate, tripotassium phosphate, triammonium phosphate, disodium phosphate, disodium phosphate, diammonium phosphate, sodium carbonate, potassium carbonate, ammonium carbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, ammonium hydrogencarbonate, sodium borate, potassium borate and ammonium borate, potassium citrate, tripotassium citrate, and sodium citrate.

Other preferable examples thereof include an organic alkali agent, for example, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, n-butylamine, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, ethyleneimine, ethylenediamine and pyridine.

These alkali agents may be used individually or in combination of two or more thereof.

Of the alkali agents, sodium hydroxide and potassium hydroxide are preferred. The reason for this is that a pH of the developer can be adjusted over a wide region by controlling an amount of the alkali agent added with respect to the nonreducing sugar. Also, trisodium phosphate, tripotassium phosphate, sodium carbonate and potassium carbonate are preferred because of their own buffering activity.

The development replenisher of the invention comprises at least one selected from the group consisting of carboxyalkylthiosuccinic anhydride, carboxyalkyl thiosuccinic acid and salts thereof incorporated therein.

Examples of the at least one selected from the group consisting of carboxyalkylthiosuccinic anhydride, carboxyalkyl thiosuccinic acid and salts thereof include compounds represented by the following general formulae (I) and (II). The developer of the invention may comprise these compounds incorporated therein singly or in combination of two or more thereof.

wherein R¹ represents a C₁-C₃₀ alkylene group; and M¹ represents a hydrogen atom, metal atom or ammonium.

wherein R² represents a C₁-C₃₀ alkyl group; and M², M³ and M⁴ each independently represents a hydrogen atom, metal atom or ammonium.

In the carboxyalkylthiosuccinic anhydride represented by the general formula (I) or salts thereof and the carboxyalkylthiosuccinic acid represented by the general formula (II) or salts thereof, R¹ and R² each independently represents a C₁-C₃₀ alkylene group which may be straight-chain or branched. Specific examples of the alkylene group include ethylene group, propylene group, butylene group, pentylene group, hexylene group, octylene group, nonylene group, decylene group, undecylene group, dodecylene group, tridecylene group, tetradecylene group, pentadecylene group, hexadecylene group, heptadecylene group, octadecylene group, nonadecylene group, eicosylene group, heneicosylene group, docosylene group, tricosylene group, tetracosylene group, pentacosylene group, hexacosylene group, octacosylene group, nonacosylene group, and triacontylene group. Preferred among these compounds are C₁-C₁₈ alkylene groups.

In the general formulae (I) and (II), the metal atoms represented by M¹, M², M³ and M⁴ each are a metal atom to monovalency. Specific examples of the metal atom include monovalent atoms which are alkaline metals such as lithium, sodium and potassium, calcium, magnesium, zinc, aluminum, iron, cobalt, nickel, copper, and tin. Preferred among these metal atoms are lithium, sodium, potassium, calcium and magnesium. Referring to a metal atom having a valence of 2 or more, an imaginary metal atom obtained by dividing the metal atom by the valency thereof is defined to be a metal atom corresponding to monovalency. For example, when a divalent metal such as calcium and magnesium is used, the metal atom corresponding to monovalency is represented, e.g., by Ca_(1/2), Mg_(1/2) or the like. When a trivalent metal such as aluminum is used, the metal atom corresponding to monovalency is represented, e.g., by A_(1/3). Actually speaking, in the compound represented by the general formula (I), when a divalent metal atom is used, one such metal atom crosslinks two molecules. When a trivalent metal atom is used, one such metal atom crosslinks three molecules. On the other hand, in the compound represented by the general formula (II), one divalent metal atom corresponding to two of M², M³ and M⁴. The divalent metal atom may correspond to two of M², M³ and M⁴ in one molecule of the compound represented by the general formula (II) or in two molecules of the compound represented by the general formula (II). In the latter case, the divalent metal atom crosslinks two molecules.

Further, the trivalent metal atom corresponds to three of M², M³ and M⁴ in one to three molecules of the compound represented by the general formula (II).

In the general formulae (I) and (II), the ammoniums represented by M¹, M², M³ and M⁴ include NH₄ ⁺, primary ammonium, secondary ammonium, and tertiary ammonium. In the primary ammonium, secondary ammonium and tertiary ammonium, the substituent may be a C₁-C₂₄ aliphatic or aromatic group which may have substituents such as hydroxyl group. In the secondary or tertiary ammonium, the various 2-substituted and 3-substituted groups may be the same or different or may be connected to each other to form a ring.

Examples of the organic amine from which the aforementioned ammonium salt is derived include aliphatic amines such as methylamine, ethylamine, propylamine, butylamine, hexylamine and octylamine, alkanolamines such as ethanolamine, diethanolamine, triethanolamine, isopropanolamine, diisopropanolamine and triisopropanolamine, aromatic amines such as aniline, and heterocyclic amines such as morpholine, pyridine, pyrrolidine and piperidine. Preferred among these organic amines are morpholine and alkanolamine.

The compound represented by the general formula (I) or (II) to be used in the invention can be produced by any ordinary method as disclosed in JP-A-8-337891. For example, by adding a mercaptocarboxylic acid or its salt to maleic anhydride, the carboxyalkylthiosuccinic anhydride or carboxyalkylthiosuccinic anhydride salt represented by the general formula (I) can be obtained. By subjecting the compound represented by the general formula (I) thus obtained to hydrolysis and optionally neutralizing the compound thus obtained with a proper basic compound to form a salt, the compound represented by the general formula (II) can be obtained.

The content of at least one selected from the group consisting of carboxyalkylthiosuccinic anhydride, carboxyalkylthiosuccinic acid and salts thereof in the developer of the invention is preferably from 0.001% to 10.0% by mass, more preferably from 0.01% to 1.0% by mass, even more preferably from 0.05% to 0.5% by mass.

As the alkaline developer there is used a developer comprising an alkali silicate or nonreducing sugar and a base as described above. Li⁺, Na⁺, K⁺ or NH₄ ⁺ is conventionally used as a cation component therein. In particular, a system containing a large amount of cation having a small ionic radius has high penetrability into an image recording layer and excellent developing property, but the system dissolves even the image area to cause image defect. Accordingly, the increase of alkali concentration has a limit to a certain extent and in order to completely perform the processing so as not to remain the image recording layer in the non-image area (residual film) without forming the defects in the image area, delicate setting of liquid conditions is required.

However, when a cation having a large ionic radius is used as the cation component, the developer can be prevented from penetration into the image recording layer and the effect of inhibiting dissolution of the image area can be enhanced without decreasing the alkali concentration, that is, the developing property.

As the cation component, cations other than the above-described alkali metal cation and ammonium ion may be used.

How the developer of the invention is used is not specifically limited.

In recent years, automatic developing machines for printing plate have bee widely used in the art of plate making/printing for the purpose of rationalizing and standardizing the plate-making job. The present developer can be used in the development by automatic developing machine.

Such an automatic developing machine normally comprises a development portion and a post-processing portion. The automatic developing machine is equipped with devices for conveying printing plate precursor, various processing tanks and spraying devices. In this arrangement, an exposed printing plate precursor is sprayed with various processing solutions pumped by a pump through a spray nozzle while being horizontally conveyed so that it is subjected to development. In recent years, a method has been known which comprises conveying a printing plate precursor while being dipped in a processing solution tank filled with a processing solution over submerged guide rolls, etc. In accordance with this automatic processing system, processing can be effected while the various processing solutions being replenished with a replenisher according to processing rate, processing time, etc.

In this case, by adding an aqueous solution having a higher alkali strength than the development starting solution to the developer as a development replenisher, a large amount of an image-forming material can be processed without replacing the developer during in the developing tank over an extended period of time. The plate-making process of the invention, too, is a preferred embodiment in which this replenishment system can be employed.

The developer may comprise various surface active agents or organic solvents incorporated therein for the purpose of accelerating or inhibiting developing properties and enhancing the dispersibility of development scum and the ink-receptivity of printing plate image area.

As the surface active agent there may be selected from the group consisting of nonionic, anionic, cationic and amphoteric surface active agents.

Examples of the nonionic surface active agent include polyethylene glycols such as polyethylene glycol and polyethylene glycol polypropylene glycol block copolymer, polyethylene glycol alkyl ethers such as polyethylene glycol cetyl ether, polyethylene glycol stearyl ether, polyethylene glycol oleyl ether and polyethylene glycol behenyl ether, polyethylene glycol polypropylene glycol alkyl ethers such as polyethylene glycol decyl tetradecyl ether and polyethylene glycol polypropylene glycol decyl tetradecyl ether, polyethylene glycol alkyl phenyl ethers such as polyethylene glycol octyl phenyl ether and polyethylene glycol nonyl phenyl ether, polyethylene glycol aliphatic acid esters such as monostearic acid ethylene glycol, distearic acid ethylene glycol, stearic acid diethylene glycol, distearic acid polyethylene glycol, monolauric acid polyethylene glycol, monostearic acid polyethylene glycol and monooleic acid polyethylene glycol, glyceryl aliphatic acid esters such as monomyristic acid glyceryl, monostearic acid glyceryl, monoisostearic acid glyceryl, distearic acid glyceryl, monooleic acid glyceryl and dioleic acid glyceryl, polyethylene oxide addition products thereof, sorbitan aliphatic acid esters such as monopalmitic acid sorbitan, monostearic acid sorbitan, tristearic acid sorbitan, monooleic acid sorbitan and trioleic acid sorbitan, polyethylene oxide addition products thereof, sorbit aliphatic acid esters such as monolauric acid sorbit, tetrastearic acid sorbit, hexastearic acid sorbit and tetraoleic acid sorbit, polyethylene oxide addition products thereof, and polyethylene oxide addition products of castor oil.

Preferred examples of the anionic surface active agent include aliphatic acid salts, abietic acid salts, hydroxyalkanesulfonic acid salts, alkanesulfonic acid salts, dialkylsulfosuccinic acid esters, α- olefinsulfonic acid salts, straight-chain alkylbenzene sulfonic acid salts, branched alkylbenzenesulfonic acid salts, alkylnaphthalenesulfonic acid salts, alkylphenoxypolyoxyethylenepropylsulfonic acid salts, polyoxyethylenealkylsulfophenyl ethers, N-methyl-N- oleyltaurine sodium salt, disodium salt of monoamide N-alkylsulfosuccinate, petroleum sulfuric acid esters, polyoxyethylenealkylethersulfuric acid esters, aliphatic monoglyceride sulfuric acid esters, polyoxyethylenealkylphenyl ether sulfuric acid esters, polyoxyethylenestyrylphenyl ether sulfuric acid esters, alkylphosphoric acid esters, polyoxyethylene alkyl ether phosphoric acid esters, polyoxyethylenealkylphenyl ether phosphoric acid esters, partial saponification product of styrene/maleic anhydride copolymer, partial saponification product of olefin/maleic anhydride, and naphthalenesulfonic acid salt-formalin condensates.

Examples of the cationic surface active agent include quaternary ammonium salts such as alkylamine salt and tetrabutyl ammonium bromide, polyoxyethylene alkylamine salts, and polyethylene polyamide derivatives.

Examples of the amphoteric surface active agent include carboxybetaines, alkylaminocarboxylic acids, sulfobetaines, aminosulfuric acid esters, and imidazolines.

The concentration of surface active agent in the developer is preferably from 0.001% to 10% by mass, more preferably from 0.005% to 1% by mass, most preferably from 0.01% to 0.5% by mass.

The developer of the invention may further comprise the following additives incorporated therein for the purpose of enhancing the developing properties thereof.

Examples of the additive include a neutral salt such as NaCl, KCl and KBr described in JP-A-58-75152, a chelating agent such as EDTA and NTA described in JP-A-58-190952, a complex such as [Co(NH₃)₆]Cl₃ and CoCl₂.6H₂O described in JP-A-59-121336, a anionic or amphoteric surfactant such as sodium alkylnaphthalenesulfonate and N-tetradecyl-N,N-dihydroxyethyl betaine described in JP-A-50-51324, a nonionic surfactant such as tetramethyldecynediol described in U.S. Pat. No. 4,374,920, a cationic polymer such as methyl chloride quaternary compound of p-dimethylaminomethyl polystyrene described in JP-A-55-95946, an amphoteric polymer electrolyte such as copolymer of vinylbenzyltrimethylammonium chloride and sodium acrylate described in JP-A-56-142528, a reducing inorganic salt such as sodium sulfite described in JP-A-57-192951, an inorganic lithium compound such as lithium chloride described in JP-A-58-59444, an organic metal surface active agent containing organic Si, Ti or the like described in JP-A-59-75255, an organic boron compound described in JP-A-59-84241, and a quaternary ammonium salt such as tetraalkylammonium oxide described in EP-101,010.

As the organic solvent to be incorporated in the developer there is preferably used benzyl alcohol. Other preferred examples of the organic solvent to be incorporated in the developer include polyethylene glycols, derivatives thereof, polypropylene glycol, and derivatives thereof.

If necessary, the developer may comprise hydroquinone, resorcin, an inorganic salt-based reducing agent such as sodium or potassium salt of sulfurous acid or hydrogensulfurous acid, an organic carboxylic acid, an anti-foaming agent or a water hardening agent incorporated therein.

The alkaline developer of the invention can be used in the development of various photosensitive lithographic printing plate precursors.

Accordingly, the invention is intended for a method which comprises exposing a photosensitive lithographic printing plate precursor, and then developing the photosensitive lithographic printing plate precursor thus exposed with the aforementioned alkaline developer.

Examples of the photosensitive lithographic printing plate precursor to which the alkaline developer of the invention can be applied include various photosensitive lithographic printing plate precursors comprising an image-recording layer such as photosensitive layer and heat-sensitive layer provided on a support. Preferred examples of these photosensitive lithographic printing plate precursors include conventional positive-working photosensitive lithographic printing plate precursors, conventional negative-working photosensitive lithographic printing plate precursors, photopolymer type photosensitive lithographic printing plate precursors, thermal positive-working photosensitive lithographic printing plate precursors, thermal positive-working photosensitive lithographic printing plate precursors. The term “conventional” as used herein is meant to indicate a conventional type lithographic printing plate precursor which is imagewise exposed through a transparent positive or negative image.

These various image-recording layers will be further described hereinafter.

<Conventional Positive-Working Photosensitive Resin>

As a conventional positive-working photosensitive resin composition there is preferably used a composition comprising a o-quinonediazide compound and an alkali-soluble polymer compound. Examples of the o-quinonediazide compound include ester of 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride with phenol-formaldehyde resin or cresol-formaldehyde resin, and ester of 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride with pyrogallol-acetone resin disclosed in U.S. Pat. No. 3,635,709. Examples of the alkali-soluble polymer compound include phenol-formaldehyde resin, cresol-formaldehyde resin, phenol-cresol-formaldehyde cocondensation resin, polyhydroxystyrene, copolymer of N-(4-hydroxyphenyl)methacrylamide, and carboxy group-containing polymer as disclosed in JP-A-7-36184. Other examples of the alkali-soluble polymer compound employable herein include various alkali-soluble polymer compounds such as acrylic resin having phenolic hydroxy group as disclosed in JP-A-51-34711, acrylic resin having sulfonamide group as disclosed in JP-A-2-866 and urethane-based resin. Further, the photosensitive resin composition preferably comprises compounds such as sensitivity adjustor, printing agent and dye disclosed in JP-A-7-92660, [0024]-[0027], and a surface active agent for improving spreadability as disclosed in the above cited patent, [0031].

<Conventional Negative-Working Photosensitive Resin>

As a conventional negative-working photosensitive resin composition there may be used a composition comprising a diazo resin and an alkali-soluble or swelling polymer compound (binder). Examples of the diazo resin include condensate of aromatic diazonium salt with active carbonyl group-containing compound such as formaldehyde. Further examples of the diazo resin include condensate of p-diazophenylamine with formaldehyde, and organic solvent-soluble diazo resin inorganic salt which is a product of reaction of hexafluorophosphate with tetrafluoroborate. In particular, a polymer diazo compound containing a hexamer in an amount of 20 mol % or more as disclosed in JP-A-59-78340 is preferably used. Preferred examples of binder include copolymers containing as essential components acrylic acid, methacrylic acid, crotonic acid or maleic acid. Specific examples of these copolymers include multi-system copolymers of monomers such as 2-hydroxyethyl (meth)acrylate, (meth)acrylonitrile and (meth)acrylic acid as disclosed in JP-A-50-118802, and multi-system copolymers composed of alkyl acrylate, (meth)acrylonitrile and unsaturated carboxylic acid as disclosed in JP-A-56-4144. Further, the photosensitive resin composition preferably comprises a compound such as printing agent, dye, plasticizer for rendering the coat layer flexible or abrasion resistant and development accelerator or a surface active agent for improving spreadability as disclosed in JP-A-7-281425, [0014]-[0015]. As the layer under the aforementioned conventional positive-working or negative-working photosensitive layer there is preferably provided an interlayer comprising a polymer compound having a constituent component having an acid group and a constituent component having an onium group as disclosed in JP-A-2000-105462.

<Photopolymer Type>

(Photosensitive Layer)

The photopolymer type photopolymerizable photosensitive composition (hereinafter referred to as “photopolymerizable composition”) comprises an addition-polymerizable ethylenically unsaturated bond-containing compound (hereinafter simply referred to as “ethylenically unsaturated bond-containing compound”), a photopolymerization initiator and a polymer binder as essential components and optionally various compounds such as coloring agent, plasticizer and heat polymerization inhibitor.

The ethylenically unsaturated bond-containing compound to be incorporated in the photopolymerizable composition is a compound having an ethylenically unsaturated bond which undergoes addition polymerization by the action of a photopolymerization initiator to cause crosslinking and curing when the photopolymerizable composition is irradiated with active light rays. The ethylenically unsaturated bond-containing compound can be freely selected from the group consisting of compounds having at least one, preferably two or more terminal ethylenically unsaturated bonds. These compounds may be in a chemical morphology such as monomer, prepolymer (e.g., dimer, trimer, oligomer), mixture thereof and copolymer thereof. Examples of the monomer include ester of unsaturated carboxylic acids (e.g., acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid) with aliphatic polyvalent alcohol compound, and amide of unsaturated carboxylic acid with aliphatic polyvalent amine compound. Also preferred are urethane-based addition-polymerizable compounds.

As the initiator to be incorporated in the photopolymerizable composition there may be properly selected from various photopolymerization initiators and system of two or more photopolymerization initiators in combination (photoinitiating system). The photoinitiating system as disclosed in JP-A-2001-22079, [0021]-[0023], is preferred. Since the polymer binder to be incorporated in the photopolymerizable composition needs to not only act as a film-forming agent for photopolymerizable composition but also cause the photosensitive layer to be dissolved in the alkaline developer, an organic polymer that can be dissolved in or swell with an alkaline aqueous solution is used as the polymer binder. As such a polymer there can be used one disclosed in the above cited patent, [0036]-[0063]. The photopolymerizable composition preferably further comprises additives disclosed in the above cited patent, [0079]-[0088], (e.g., surface active agent for improving spreadability) incorporated therein.

An oxygen-shielding protective layer is preferably provided on the aforementioned photosensitive layer to prevent oxygen from inhibiting polymerization. Examples of the polymer to be incorporated in the oxygen-shielding protective layer include polyvinyl alcohols and copolymers thereof. As the subbing layer for the photopolymer type photosensitive layer there is preferably provided an interlayer or adhesive layer as disclosed in JP-A-2001-228608, [0124]-[0165].

<Thermal Positive-Working Photosensitive Composition>

(Heat-Sensitive Layer)

The thermal positive-working heat-sensitive layer comprises an alkali-soluble polymer compound and a photo-heat converting material. Examples of the alkali-soluble polymer compound include homopolymers comprising an acidic group incorporated in polymer, copolymers thereof, and mixtures thereof. In particular, those having an acidic group such as the following compounds (1) and (2) are preferred from the standpoint of solubility in the alkaline developer. (1) Phenolic hydroxyl group (—Ar—OH); and (2) Sulfonamide group (—SO2NH—R). Particularly preferred among these compounds is phenolic hydroxyl group from the standpoint of excellence in capability of forming an image by exposure to infrared laser beam. Preferred examples of the phenolic hydroxyl group include novolak resins such as phenol formaldehyde resin, m-cresol formaldehyde resin, p-cresol formaldehyde resin, in-/p-mixed cresol formaldehyde resin and phenol/cresol (any of m-, p-and m-/p- mixed) mixed formaldehyde resin, and pyrogallol acetone resins. In some detail, polymers disclosed in JP-A-2001-305722, [0023]-[0042], are preferably used. The photo-heat converting material can convert exposure energy to heat so as to efficiently release the mutual action of the exposed area on the heat-sensitive layer. From the standpoint of recording sensitivity, a pigment or dye having a light absorption range in an infrared range of from 700 nm to 1,200 nin is preferred. Specific examples of the dye employable herein include dyes such as azo dye, metal complex-based azo dye, pyrazolone- based azo dye, naphthoquinone dye, anthraquinone dye, phthalocyanine dye, carbonium dye, quinonimine dye, methine dye, cyanine dye, squarylium dye, pyrylium salt and metal thiolate complex (e.g., nickel thiolate complex). Preferred among these dyes is cyanine dye. Examples of the cyanine dye include those represented by the general formula (I) in JP-A-2001-305722. The thermal positive-working composition preferably comprises the same sensitivity adjustor, printing agent, dye and other compounds or surface active agent for improving spreadability as described above with reference to conventional positive-working photosensitive composition. In some detail, compounds as disclosed in JP-A-2001-305722, [0053]-[0059], are preferred.

The thermal positive-working heat-sensitive layer may be in a single layer form or a two-layer form as disclosed in JP-A-11-218914.

An undercoating layer is preferably provided interposed between the thermal positive-working heat-sensitive layer and the support. Examples of the components to be incorporated in the undercoating layer include various organic compounds disclosed in JP-A-2001-305722, [0068].

<Thermal Negative-Working Photosensitive Composition>

(Heat-Sensitive Layer)

The thermal negative-working photosensitive layer is a negative-working heat-sensitive layer which cures on the area irradiated with infrared laser beam to form an image area.

A preferred example of the thermal negative-working heat-sensitive layer is a polymerizable layer. The polymerizable layer comprises (A) an infrared absorber, (B) a radical generator (radical polymerization initiator), (C) a radical polymerizable compound which undergoes polymerization reaction with the radical generator thus generated, and (D) a binder polymer.

In the polymerizable layer, the infrared light rays which have been absorbed by the infrared absorber are converted to heat by which the radical polymerization initiator such as onium is decomposed to generate radical. The radical-polymerizable compound is selected from the group consisting of compounds having terminal ethylenically unsaturated bond. The radical-polymerizable compound starts to undergo chain polymerization reaction with the radical generated so that it is cured. Examples of the infrared absorber (A) include the aforementioned photo-heat converting material to be incorporated in the aforementioned thermal positive-working heat-sensitive layer. In particular, specific examples of the cyanine dye include those disclosed in JP-A-2001-133969, [0017]-[0019]. Specific examples of the radical generator (B) include onium salts. Specific preferred examples of the onium salts employable herein include those disclosed in JP-A-2001-133969, [0030]-[0033]. The radical-polymerizable compound (C) can be selected from the group consisting of compounds having at least one, preferably two or more terminal ethylenically unsaturated bonds. As the binder polymer (D) there is preferably used a linear organic polymer. As such a linear organic polymer there is selected a linear organic polymer which can be dissolved in or swells with water or weak aqueous alkali. Particularly preferred among these linear organic polymers are (meth)acrylic resins having benzyl group or allyl group and carboxyl group in its side chain because they provide well-balanced film strength, sensitivity and developing properties. For the details of the radical-polymerizable compound (C) and the binder polymer (D), reference can be made to the above cited JP-A-2001-133969, [0036]-[0060]. As other additives, those (e.g., surface active agent for improving spreadability) disclosed in the above cited JP-A-2001-133969, [0061]-[0068], are preferably added.

Preferred examples of the thermal negative-working heat-sensitive layer other than polymerizable layer include acid-crosslinkable layer. The acid-crosslinkable layer comprises (E) a compound which generates an acid when irradiated with light or heated (hereinafter referred to as “acid generator”), (F) a compound which undergoes crosslinking with the acid thus generated (hereinafter referred to as “crosslinking agent”), and (G) an alkali-soluble polymer compound capable of reacting with the crosslinking agent in the presence of an acid. In order to make efficient use of the energy of infrared laser beam, the acid-crosslinkable layer comprises (A) an infrared absorber incorporated therein. Examples of the acid generator (E) include compounds which can be thermally decomposed to generate an acid, such as photopolymerization initiator, dye photodecoloring agent and acid generator used in microresist. Examples of the crosslinking agent (F) include (i) aromatic compounds substituted by hydroxymethyl group or alkoxymethyl group, (ii) compounds having N-hydroxymethyl group, N-alkoxymethyl group or N-acyloxymethyl group, and (iii) epoxy compounds. Examples of the alkali-soluble polymer compound (G) include novolak resins, and polymers having hydroxyaryl group in its side chain.

<Back Coat Layer>

The photosensitive lithographic printing plate precursor obtained by laminating various image recording layers may optionally comprise a coat layer made of an organic polymer compound (referred to as “back coat layer”) provided on the back side thereof to prevent the image recording layers from being scratched when it is superposed on each other.

<Exposure>

The photosensitive lithographic printing plate precursor is subjected to imagewise exposure by various processing methods according to the image recording layer incorporated therein. Examples of the light source for actinic ray used for the imagewise exposure include mercury lamp, metal halide lamp, xenon lamp, and chemical lamp. Examples of the laser beam include helium-neon laser (He—Ne laser), argon laser, krypton laser, helium-cadmium laser, KrF excimer laser, semiconductor laser, YAG laser, and YAG-SHG laser.

The alkaline developer of the invention is preferably used particularly in the making of a printing plate from infrared-sensitive lithographic printing plate precursor. Accordingly, reference will be made to a method of producing a lithographic printing plate which comprises subjecting an infrared-sensitive lithographic printing plate precursor comprising a photosensitive layer (hereinafter also referred to as “heat-sensitive layer”) containing an infrared-absorbing dye and an alkali-soluble resin provided on a support to exposure, and then developing the infrared-sensitive lithographic printing plate precursor thus exposed with the alkaline developer described in detail above.

The infrared-sensitive lithographic printing plate precursor will be further described hereinafter. Firstly, the components of the heat-sensitive layer as the image recording layer of the infrared-sensitive lithographic printing plate precursor will be described hereinafter.

[Infrared Absorbing Dye]

In the present invention, the infrared absorbing dye used for the heat-sensitive layer is not particularly limited as long as it is a dye capable of absorbing infrared ray to generate heat, and various dyes known as infrared absorbing dyes can be used.

As for the infrared absorbing dye, commercially available dyes and known dyes described in publications (for example, Senryo Binran (Handbook of Dyes), compiled by Yuki Gosei Kagaku Kyokai (1970)) may be used. Specific examples thereof include dyes, for example, azo dye, metal complex azo dye, pyrazolone azo dye, quinoneimine dye, methine dye and cyanine dye. Among these, dyes capable of absorbing infrared or near infrared ray are preferred in the present invention, because such dyes are suitable for use with a laser emitting infrared or near infrared ray.

Examples of the dye capable of absorbing infrared or near infrared ray include cyanine dyes described in JP-A-58-125246, JP-A-59-84356, JP-A-59-202829 and JP-A-60-78787, methine dyes described in JP-A-58-173696, JP-A-58-181690 and JP-A-58-194595, naphthoquinone dyes described in JP-A-58-112793, JP-A-58-224793, JP-A-59-48187, JP-A-59-73996, JP-A-60-52940 and JP-A-60-63744, squarylium dyes described in JP-A-58-112792, and cyanine dyes described in British Patent 434,875.

Furthermore, near infrared absorbing sensitizers described in U.S. Pat. No. 5,156,938 may also be preferably used as the dye. In particular, substituted arylbenzo(thio)pyrylium salts described in U.S. Pat. No. 3,881,924, trimethinethiapyrylium salts described in JP-A-57-142645 (corresponding to U.S. Pat. No. 4,327,169), pyrylium-based compounds described in JP-A-58-181051, JP-A-58-220143, JP-A-5941363, JP-A-59-84248, JP-59-84249, JP-A-59-146063 and JP-A-59-146061, cyanine dyes described in JP-A-59-216146, pentamethinethiapyrylium salts described in U.S. Pat. No. 4,283,475, pyrylium compounds described in JP-B-5-13514 (the term “JP-B” as used herein means an “examined Japanese patent publication”) and JP-B-5-19702, and commercially available products, for example, Epolight III-178, Epolight III-130 and Epolight III-125 produced by Epolin Inc. are preferably used.

Particularly preferred examples of the infrared absorbing dye for use in the heat-sensitive layer include infrared absorbing dyes represented by formulae (I) and (II) of U.S. Pat. No. 4,756,993. The dye very strongly interacts with an alkali-soluble resin and assures excellent alkali development resistance in the unexposed area of the heat-sensitive layer.

The amount of the infrared-absorbing dye to be incorporated in the heat-sensitive layer is from 3% to 50% by mass, preferably from 5% to 40% by mass, more preferably from 8% to 35% by mass based on the weight of the heat-sensitive layer in view of sensitivity and durability of the heat-sensitive layer.

Specific examples of the infrared-absorbing dye will be given below, but the invention is not limited thereto.

[Alkali-Soluble Resin]

The alkali-soluble resin for use in the heat-sensitive layer is a water-insoluble and alkali water-soluble resin (hereinafter sometimes referred to as an “alkali-soluble polymer”) and includes homopolymers containing an acidic group in the main chain and/or side chain thereof, copolymers thereof and mixtures thereof. Accordingly, the heat-sensitive layer of the photosensitive lithographic printing plate precursor has a property of being dissolved when brought into contact with an alkaline developer.

As for the alkali-soluble polymer for use in the heat-sensitive layer, hitherto known alkali-soluble polymers are employed without particular limitation, but it is preferably a polymer having any functional group of (1) a phenolic hydroxy group, (2) a sulfonamido group and (3) an active imido group in its molecule. Examples thereof include those described below, but the present invention should not be construed as being limited thereto.

Examples of the polymer compound having (1) a phenolic hydroxy group include a novolak resin, for example, phenol-formaldehyde resin, m-cresol-formaldehyde resin, p-cresol-formaldehyde resin, m-/p-mixed cresol-formaldehyde resin or phenol/(m-, p- or m-/p-mixed) cresol mixed formaldehyde resin, and a pyrogallol acetone resin. In addition, a polymer compound having a phenolic hydroxy group in its side chain is preferably used as the polymer compound having a phenolic hydroxy group. Examples of the polymer compound having a phenolic hydroxy group in the side chain thereof include a polymer compound obtained by homopolymerizing a polymerizable monomer of a low molecular compound having at least one phenolic hydroxy group and at least one polymerizable unsaturated bond, or by copolymerizing the monomer with another polymerizable monomer.

Examples of the polymerizable monomer having a phenolic hydroxy group include an acrylamide, a methacrylamide, an acrylic acid ester and a methacrylic acid ester each having a phenolic hydroxyl group and a hydroxystyrene. Specific preferred examples thereof include N-(2-hydroxyphenyl)acrylamide, N-(3-hydroxyphenyl)acrylamide, N-(4-hydroxyphenyl)acrylamide, N-(2-hydroxyphenyl)methacrylamide, N-(3-hydroxyphenyl)methacrylamide, N-(4-hydroxyphenyl)methacrylamide, o-hydroxyphenyl acrylate, m-hydroxyphenyl acrylate, p-hydroxyphenyl acrylate, o-hydroxyphenyl methacrylate, m-hydroxyphenyl methacrylate, p-hydroxyphenyl methacrylate, o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene, 2-(2-hydroxyphenyl)ethyl acrylate, 2-(3-hydroxyphenyl)ethyl acrylate, 2-(4-hydroxyphenyl)ethyl acrylate, 2-(2-hydroxyphenyl)ethyl methacrylate, 2-(3-hydroxyphenyl)ethyl methacrylate and 2-(4-hydroxyphenyl)ethyl methacrylate. The resins having a phenolic hydroxy group may be used in combination of two or more thereof. Furthermore, as described in U.S. Pat. No. 4,123,279, a copolymer of formaldehyde and phenol containing as a substituent, an alkyl group having from 3 to 8 carbon atoms, for example, tert-butyl phenol formaldehyde resin or octyl phenol formaldehyde resin, may be used in combination.

Examples of the alkali-soluble polymer compound having (2) a sulfonamido group include a polymer compound obtained by homopolymerizing a polymerizable monomer having a sulfonamido group, or by copolymerizing the monomer with another polymerizable monomer. Examples of the polymerizable monomer having a sulfonamido group include a polymerizable monomer of a low molecular compound having at least one polymerizable unsaturated bond and at least one sulfonamido group where at least one hydrogen atom is bonded on the nitrogen atom (—NH—SO₂—) per molecule. Among these, preferred are low molecular compounds having an acryloyl, aryl or vinyloxy group and an unsubstituted or mono-substituted aminosulfonyl group or a substituted sulfonylimino group.

The alkali-soluble polymer compound having (3) an active imido group is preferably a polymer compound having an active imido group in its molecule, and examples of the polymer compound include a polymer compound obtained by homopolymerizing a polymerizable monomer of a low molecular compound having at least one active imido group and at least one polymerizable unsaturated bond per molecule, or by copolymerizing the monomer with another polymerizable monomer.

Specific examples of the polymer compound which can be preferably used include N-(p-toluenesulfonyl)methacrylamide and N-(p-toluenesulfonyl)acrylamide.

The alkali-soluble polymer compound is preferably a polymer compound obtained by polymerizing two or more of the above-described polymerizable monomers having a phenolic hydroxy group, polymerizable monomers having a sulfonamido group and polymerizable monomers having an active imido group, or a polymer compound obtained by copolymerizing two or more of these polymerizable monomers with another polymerizable monomer. In the case of copolymerizing a polymerizable monomer having a phenolic hydroxy group with a polymerizable monomer having a sulfonamido group and/or a polymerizable monomer having an active imido group, a weight ratio of the components blended is preferably from 50:50 to 5:95, more preferably from 40:60 to 10:90.

In the case where the alkali-soluble polymer is a copolymer of the above-described polymerizable monomer having a phenolic hydroxy group, a sulfonamido group or an active imido group with another polymerizable monomer, the copolymer preferably contains 10% by mole or more, more preferably 20% by mole or more. In case of less than 10% by mole, alkali solubility tends to be insufficient, thus it may occur that the effect of enhancing the developing latitude is not satisfactory achieved.

Examples of the monomer component that is copolymerized with the polymerizable monomer having a phenolic hydroxy group, polymerizable monomer having a sulfonamido group or polymerizable monomer having an active imido group include the compounds shown in (m1) to (m12) below, but the present invention should not be construed as being limited thereto.

(m1) Acrylic acid esters and methacrylic acid esters each having an aliphatic hydroxy group, for example, 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate.

(m2) Alkyl acrylates, for example, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, amyl acrylate, hexyl acrylate, octyl acrylate, benzyl acrylate, 2-chloroethyl acrylate or glycidyl acrylate.

(m3) Alkyl methacrylates, for example, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, 2-chloroethyl methacrylate or glycidyl methacrylate.

(m4) Acrylamides and methacrylamides, for example, acrylamide, methacrylamide, N-methylolacrylamide, N-ethylacrylamide, N-hexylmethacrylamide, N-cyclohexylacrylamide, N-hydroxyethylacrylamide, N-phenylacrylamide, N-nitrophenylacrylamide or N-ethyl-N-phenylacrylamide.

(m5) Vinyl ethers, for example, ethyl vinyl ether, 2-chloroethyl vinyl ether, hydroxyethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, octyl vinyl ether or phenyl vinyl ether.

(m6) Vinyl esters, for example, vinyl acetate, vinyl chloroacetate, vinyl butyrate or vinyl benzoate.

(m7) Styrenes, for example, styrene, α-methylstyrene, methylstyrene or chloromethylstyrene.

(m8) Vinyl ketones, for example, methyl vinyl ketone, ethyl vinyl ketone, propyl vinyl ketone or phenyl vinyl ketone.

(m9) Olefins, for example, ethylene, propylene, isobutylene, butadiene or isoprene.

(m10) N-Vinylpyrrolidone, acrylonitrile, methacrylonitrile or the like.

(m11) Unsaturated imides, for example, maleimide, N-acryloylacrylamide, N-acetylmethacrylamide, N-propionylmethacrylamide or N-(p-chlorobenzoyl)methacrylamide.

(m12) Unsaturated carboxylic acids, for example, acrylic acid, methacrylic acid, maleic anhydride or itaconic acid.

The alkali-soluble polymer compound preferably has a phenolic hydroxy group because of excellent image forming property upon exposure with an infrared laser or the like. Preferred examples thereof include a novolak resin, for example, phenol-formaldehyde resin, m-cresol-formaldehyde resin, p-cresol-formaldehyde resin, m-/p-mixed cresol-formaldehyde resin or phenol/(m-, p- or m-/p-mixed) cresol mixed formaldehyde resin, and a pyrogallol acetone resin.

Other examples of the alkali-soluble polymer compound having a phenolic hydroxy group include condensation polymerization products of formaldehyde and phenol containing as a substituent, an alkyl group having from 3 to 8 carbon atoms, for example, tert-butyl phenol formaldehyde resin and octyl phenol formaldehyde resin, described in U.S. Pat. No. 4,123,279.

With respect to the method for copolymerization of the alkali-soluble polymer compound, a conventionally known method, for example, graft copolymerization, block copolymerization or random copolymerization can be used.

In the present invention, when the alkali-soluble polymer is a homopolymer or copolymer of the above-described polymerizable monomer having a phenolic hydroxy group, polymerizable monomer having a sulfonamido group or polymerizable monomer having an active imido group, the polymer preferably has a weight average molecular weight of 2,000 or more and a number average molecular weight of 500 or more, more preferably a weight average molecular weight of 5,000 to 300,000, a number average molecular weight of 800 to 250,000 and a dispersity (weight average molecular weight/number average molecular weight) of 1.1 to 10.

Also, in the present invention, when the alkali-soluble polymer is a resin, for example, phenol-formaldehyde resin or cresol-aldehyde resin, the polymer preferably has a weight average molecular weight of 500 to 20,000 and a number average molecular weight of 200 to 10,000.

The alkali-soluble polymer compounds may be used individually or in combination of two or more thereof. An amount of the alkali-soluble polymer compound added is from 30 to 99% by mass, preferably from 40 to 95% by mass, more preferably from 50 to 90% by mass, based on the total solid content in the heat-sensitive layer. The amount in the range described above is preferred from both aspects of durability and sensitivity of the heat-sensitive layer.

The heat-sensitive layer may also contain an alkali-soluble polymer compound having a carboxy group (hereinafter sometimes referred to as a “component (B1)”).

The polymer compound as the component (B1) may be any compound as long as it is an alkali-soluble polymer compound having a carboxy group, but polymer compounds (b1-1) and (b1-2) described below are preferred.

(b1-1) Alkali-Soluble Polymer Compound Having Polymerizable Monomer Unit Represented by Formula (i) (hereinafter sometimes referred to as a “polymer compound (b1-1)”)

(wherein Xm represents a single bond or a divalent linking group, Y represents a hydrogen atom or a carboxy group, and Z represents a hydrogen atom, an alkyl group or a carboxy group).

A monomer constituting the polymerizable monomer unit represented by formula (i) includes a polymerizable monomer containing at least one carboxy group and at least one polymerizable unsaturated group in its molecule.

Specific examples of such a polymerizable monomer include an α,β-unsaturated carboxylic acid, for example, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid or itaconic anhydride.

Examples of a monomer, which is copolymerized with the above-described polymerizable monomer having a carboxy group, include the compounds shown in (1) to (11) below, but the present invention should not be construed as being limited thereto.

(1) Acrylic acid esters and methacrylic acid esters each having an aliphatic hydroxy group, for example, 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate.

(2) Alkyl acrylates, for example, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, amyl acrylate, hexyl acrylate, octyl acrylate, benzyl acrylate, 2-chloroethyl acrylate, glycidyl acrylate or N-dimethylaminoethyl acrylate.

(3) Alkyl methacrylates, for example, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, 2-chloroethyl methacrylate, glycidyl methacrylate or N-dimethylaminoethyl methacrylate.

(4) Acrylamides and methacrylamides, for example, acrylamide, methacrylamide, N-methylolacrylamide, N-ethylacrylamide, N-hexylmethacrylamide, N-cyclohexylacrylamide, N-hydroxyethylacrylamide, N-phenylacrylamide, N-nitrophenylacrylamide or N-ethyl-N-phenylacrylamide.

(5) Vinyl ethers, for example, ethyl vinyl ether, 2-chloroethyl vinyl ether, hydroxyethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, octyl vinyl ether or phenyl vinyl ether.

(6) Vinyl esters, for example, vinyl acetate, vinyl chloroacetate, vinyl butyrate or vinyl benzoate.

(7) Styrenes, for example, styrene, α-methylstyrene, methylstyrene or chloromethylstyrene.

(8) Vinyl ketones, for example, methyl vinyl ketone, ethyl vinyl ketone, propyl vinyl ketone or phenyl vinyl ketone.

(9) Olefins, for example, ethylene, propylene, isobutylene, butadiene or isoprene.

(10) N-Vinylpyrrolidone, N-vinylcarbazole, 4-vinylpyridine, acrylonitrile, methacrylonitrile or the like.

(11) Unsaturated imides, for example, maleimide, N-acryloylacrylamide, N-acetylmethacrylamide, N-propionylmethacrylamide or N-(p-chlorobenzoyl)methacrylamide.

A monomer represented by the following formula (ii) is also preferably used.

wherein X represents O, S or N—R¹², R¹⁰ to R¹² each independently represents a hydrogen atom or an alkyl group, m, n and o each independently represents an integer of 2 to 5, C_(m)H_(2m), C_(n)H_(2n) and C_(o)H_(2o) each may be a straight chain or a branched structure, p, q and r each independently represents an integer of 0 to 3,000, provided that p+q+r≧2.

The alkyl group represented by any one of R¹⁰ to R¹² is preferably an alkyl group having from 1 to 12 carbon atoms, and specific examples thereof include a methyl group, an ethyl group, an n-propyl group and an isopropyl group. p, q and r each preferably represents an integer of 0 to 500, more preferably an integer of 0 to 100.

Examples of a monomer corresponding to the repeating unit represented by formula (ii) are set forth below, but the present invention should not be construed as being limited thereto.

(average molecular weight of alkylene oxide: 1,000)

(average molecular weight of alkylene oxide: 1,000)

(average molecular weight of alkylene oxide: 500)

(average molecular weight of alkylene oxide: 2,000)

(average molecular weight of alkylene oxide: 1,500)

The monomer corresponding to the repeating unit represented by formula (ii) can be produced by reacting a commercially available hydroxypoly(oxyalkylene) material, for example, a material available under a trade name of Pluronic (produced by Asahi Denka Co., Ltd.), Adeka Polyether (produced by Asahi Denka Co., Ltd.), Carbowax (produced by Glico Products), Toriton (produced by Rohm and Haas Co.) or P.E.G (produced by Dai-Ichi Kogyo Seiyaku Co., Ltd.), with acrylic acid, methacrylic acid, acryl chloride, methacryl chloride, acrylic anhydride or the like according to a known method.

Further, poly(oxyalkylene) diacrylate produced by a known method may also be used.

Examples of the commercially available monomer include hydroxy group-terminated polyalkylene glycol mono(meth)acrylates produced by NOF Corp., for example, Blemmer PE-90, Blemmer PE-200, Blemmer PE-350, Blemmer AE-90, Blemmer AE-200, Blemmer AE-400, Blemmer PP-1000, Blemmer PP-500, Blemmer PP-800, Blemmer AP-150, Blemmer AP-400, Blemmer AP-550, Blemmer AP-800, Blemmer 50 PEP-300, Blemmer 70 PEP-350B, Blemmer AEP Series, Blemmer 55 PET-400, Blemmer 30 PET-800, Blemmer 55 PET-800, Blemmer AET Series, Blemmer 30 PPT-800, Blemmer 50 PPT-800, Blemmer 70 PPT-800, Blemmer APT Series, Blemmer 10 PPB-500B and Blemmer 10 APB-500B; alkyl-terminated polyalkylene glycol mono(meth)acrylates produced by NOF Corp., for example, Blemmer PME-100, Blemmer PME-200, Blemmer PME-400, Blemmer PME-1000, Blemmer PME-4000, Blemmer AME-400, Blemmer 50 POEP-800B, Blemmer 50 AOEP-800B, Blemmer PLE-200, Blemmer ALE-200, Blemmer ALE-800, Blemmer PSE-400, Blemmer PSE-1300, Blemmer ASEP Series, Blemmer PKEP Series, Blemmer AKEP Series, Blemmer ANE-300, Blemmer ANE-1300, Blemmer PNEP Series, Blemmer PNPE Series, Blemmer 43 ANEP-500, Blemmer 70 ANEP-550; and monomers produced by Kyoeisha Chemical Co., Ltd., for example, Light Ester MC, Light Ester 130MA, Light Ester 041MA, Light Acrylate BO-A, Light Acrylate EC-A, Light Acrylate MTG-A, Light Acrylate 130A, Light Acrylate DPM-A, Light Acrylate P-200A, Light Acrylate NP-4EA and Light Acrylate NP-8EA.

In the polymer compound (b1-1), the minimum constituent unit comprising the polymerizable monomer component having at least one carboxy group and at least one polymerizable unsaturated group in the molecule thereof is not particularly limited to only one species, and a copolymer obtained by copolymerizing two or more minimum constituent units having the same acidic group or a copolymer obtained by copolymerizing two or more minimum constituent units differing in the acidic group contained therein may be used.

With respect to the method for copolymerization, a conventionally known method, for example, graft copolymerization, block copolymerization and random copolymerization can be used.

(b1-2) Carboxyl Group-Containing Alkali-Soluble Polymer Compound Including as Basic Skeleton, Reaction Product of Diol Compound Having Carboxy Group Represented by Formula (iii), (iv) or (v) and Diisocyanate Compound Represented by Formula (viii) (hereinafter sometimes referred to as a “polymer compound (b 1-2)”)

In the formulae, R¹³ represents a hydrogen atom or an alkyl, alkenyl, aralkyl, aryl, alkoxy or aryloxy group which may have a substituent (preferably including, for example, an alkyl group, an aryl group, an alkoxy group, an ester group, a urethane group, an amido group, a ureido group or a halogeno group), and preferably represents a hydrogen atom, an alkyl group having from 1 to 8 carbon atoms, an alkenyl group having from 2 to 8 carbon atoms or an aryl group having from 6 to 15 carbon atoms.

R⁴, R¹⁵ and R¹⁶, which may be the same or different, each represents a single bond or a divalent aliphatic or aromatic hydrocarbon group which may have a substituent (preferably including, for example, an alkyl group, an alkenyl group, an aralkyl group, an aryl group, an alkoxy group or a halogeno group), preferably represents an alkylene group having from 1 to 20 carbon atoms or an arylene group having 6 to 15 carbon atoms, and more preferably represents an alkylene group having from 1 to 8 carbon atoms.

If desired, R¹⁴, R¹⁵ and R¹⁶ each may contain another functional group that does not react with the isocyanate group, for example, an ester group, a urethane group, an amido group, a ureido group or a carbon-carbon unsaturated bond. Two or three of R¹³, R¹⁴, R¹⁵ and R¹⁶ may form a ring.

Ar represents a trivalent aromatic hydrocarbon group which may have a substituent, and preferably represents an aromatic group having from 6 to 15 carbon atoms. OCN—R¹⁸—NCO  (viii) wherein R¹⁸ represents a divalent aliphatic or aromatic hydrocarbon group which may have a substituent (preferably including, for example, an alkyl group, an alkenyl group, an aralkyl group, an aryl group, an alkoxy group or a halogeno group). If desired, R¹⁸ may contain another functional group that does not react with the isocyanate group, for example, an ester group, a urethane group, an amido group, a ureido group or a carbon-carbon unsaturated bond.

Specific examples of the diol compound having a carboxy group represented by formulae (iii), (iv) or (v) include:

3,5-dihydroxybenzoic acid, 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(2-hydroxyethyl)propionic acid, 2,2-bis(3-hydroxypropyl)propionic acid, bis(hydroxymethyl)acetic acid, bis(4-hydroxyphenyl)acetic acid, 4,4-bis(4-hydroxyphenyl)pentanoic acid, tartaric acid and N,N-bis(2-hydroxyethyl)-3-carboxypropionamide.

The carboxyl group-containing alkali-soluble polymer compound (b1-2) is preferably a reaction product combined with a diol represented by the following formula (vi) or (vii):

wherein each R¹⁷ represents a hydrogen atom or an alkyl group having from 1 to 8 carbon atoms, and n represents an integer of 2 or more. Examples of the alkyl group having from 1 to 8 carbon atoms for R¹⁷ include a methyl group, an ethyl group, an isopropyl group, an n-butyl group and an isobutyl group.

Specific examples of the diol represented by formula (vi) or (vii) are set forth below, but the present invention should not be construed as being limited thereto.

Specific examples of (vi):

HO—(—CH₂CH₂O—)₃—H

HO—(—CH₂CH₂O—)₄—H

HO—(—CH₂CH₂O—)₅—H

HO—(—CH₂CH₂O—)₆—H

HO—(—CH₂CH₂O—)_(r)H

HO—(—CH₂CH₂O—)₈—H

HO—(—CH₂CH₂O—)₁₀—H

HO—(—CH₂CH₂O—)₁₂—H

Polyethylene glycol (average molecular weight: 1,000)

Polyethylene glycol (average molecular weight: 2,000)

Polyethylene glycol (average molecular weight: 4,000)

HO—(—CH₂CH(CH₃)O—)₃—H

HO—(—CH₂CH(CH₃)O—)₄—H

HO—(—CH₂CH(CH₃)O—)₆—H

Polypropylene glycol (average molecular weight: 1,000)

Polypropylene glycol (average molecular weight: 2,000)

Polypropylene glycol (average molecular weight: 4,000)

Specific examples of (vii):

HO—(—CH₂CH₂CH₂O—)₃—H

HO—(—CH₂CH₂CH₂O—)₄—H

HO—(—CH₂CH₂CH₂O—)₈—H

HO—(—CH₂CH₂CH(CH₃)O—)₁₂—H

Specific examples of the diisocyanate compound represented by formula (viii) include:

aromatic diisocyanate compound, for example, 2,4-tolylene diisocyanate, dimer of 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, 4,4′-diphenyl methane diisocyanate, 1,5-naphthalene diisocyanate or 3,3′-dimethylbiphenyl-4,4′-diisocyanate; aliphatic diisocyanate compound, for example, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate or dimeric acid diisocyanate; aliphatic diisocyanate compound, for example, isophorone diisocyanate, 4,4′-methylenebis(cyclohexyl isocyanate), methylcyclohexane-2,4(or 2,6)-diisocyanate or 1,3-(isocyanatomethyl)cyclohexane; and diisocyanate compound obtained by a reaction of diol with diisocyanate, for example, an adduct of 1 mol of 1,3-butylene glycol and 2 mol of tolylene diisocyanate.

A molar ratio of the diisocyanate and the diol compound used for synthesis of the polymer compound (b1-2) is preferably from 0.8:1 to 1.2 to 1, and when an isocyanate group is remaining at the polymer terminal, such a compound is treated with an alcohol or an amine so that a compound having no residual isocyanate group can be finally synthesized.

In the component (B1), one compound selected from the polymer compounds (b1-1) and (b 1-2) may be used alone, or two or more thereof may be used in combination.

A content of the carboxyl group-containing repeating unit contained in the component (B1) is 2% by mole or more, preferably from 2 to 70% by mole, more preferably from 5 to 60% by mole, based on the total amount of respective monomers in the component (B1).

A weight average molecular weight of the component (B1) is preferably from 3,000 to 300,000, more preferably from 6,000 to 100,000.

An amount of the component (B1) added is preferably from 0.005 to 80% by mass, more preferably from 0.01 to 50% by mass, still more preferably from 1 to 20% by mass, based on the total solid content of the heat-sensitive layer.

[Additives]

In the formation of the heat-sensitive layer, various additives may be added, if desired, in addition to the above-described components as long as the effects of the present invention are not impaired.

-Solubility Inhibiting Compound-

In the photosensitive lithographic printing plate precursor, various inhibitors may be incorporated into the heat-sensitive layer in order to enhance the inhibition (solubility inhibition).

The inhibitor is not particularly limited, and examples thereof include a quaternary ammonium salt and a polyethylene glycol-based compound.

The quaternary ammonium salt is not particularly limited, and examples thereof include tetraalkylammonium salts, trialkylarylammonium salts, dialkyldiarylammonium salts, alkyltriarylammonium salts, tetraarylammonium salts, cyclic ammonium salts and dicyclic ammonium salts.

Specific examples thereof include tetrabutylammonium bromide, tetrapentylammonium bromide, tetrahexylammonium bromide, tetraoctylammonium bromide, tetralaurylammonium bromide, tetraphenylammonium bromide, tetranaphthylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium iodide, tetrastearylammonium bromide, lauryltrimethylammonium bromide, stearyltrimethylammonium bromide, behenyltrimethylammonium bromide, lauryltriethylammonium bromide, phenyltrimethylammonium bromide, 3-trifluoromethylphenyltrimethylammonium bromide, benzyltrimethylammonium bromide, dibenzyldimethylammonium bromide, distearyldimethylammonium bromide, tristearylmethylammonium bromide, benzyltriethylammonium bromide, hydroxyphenyltrimethylammonium bromide and N-methylpyridinium bromide. In particular, quaternary ammonium salts described in Japanese Patent Application Nos. 2001-226297, 2001-370059 and 2001-398047 are preferred.

An amount of the quaternary ammonium salt added is preferably from 0.1 to 50% by mass, more preferably from 1 to 30% by mass, based on the total solid content of the image recording layer. The amount in the range is appropriate from the standpoint that a sufficiently high solubility inhibiting effect is achieved and the film-forming property of binder is not deteriorated.

The polyethylene glycol-based compound is not particularly limited, and examples thereof include those having the following structure: R¹—{—O—(R³—O—)_(m)—R²}_(n) wherein R¹ represents a polyhydric alcohol residue or a polyhydric phenol residue, R² represents a hydrogen atom or an alkyl, alkenyl, alkynyl, alkyloyl, aryl or aryloyl group having from 1 to 25 carbon atoms, which may have a substituent, R³ represents an alkylene residue, which may have a substituent, m represents an integer of 10 or more on average, and n represents an integer of 1 to 4.

Examples of the polyethylene glycol-based compound having the structure shown above include polyethylene glycols, polypropylene glycols, polyethylene glycol alkyl ethers, polypropylene glycol alkyl ethers, polyethylene glycol aryl ethers, polypropylene glycol aryl ethers, polyethylene glycol alkylaryl ethers, polypropylene glycol alkylaryl ethers, polyethylene glycol glycerin esters, polypropylene glycol glycerin esters, polyethylene glycol sorbitol esters, polypropylene glycol sorbitol esters, polyethylene glycol fatty acid esters, polypropylene glycol fatty acid esters, polyethylene glycolated ethylenediamines, polypropylene glycolated ethylenediamines, polyethylene glycolated diethylenetriamines and polypropylene glycolated diethylenetriamines.

Specific examples thereof include polyethylene glycol 1000, polyethylene glycol 2000, polyethylene glycol 4000, polyethylene glycol 10000, polyethylene glycol 20000, polyethylene glycol 5000, polyethylene glycol 100000, polyethylene glycol 200000, polyethylene glycol 500000, polypropylene glycol 1500, polypropylene glycol 3000, polypropylene glycol 4000, polyethylene glycol methyl ether, polyethylene glycol ethyl ether, polyethylene glycol phenyl ether, polyethylene glycol dimethyl ether, polyethylene glycol diethyl ether, polyethylene glycol diphenyl ether, polyethylene glycol lauryl ether, polyethylene glycol dilauryl ether, polyethylene glycol nonyl ether, polyethylene glycol cetyl ether, polyethylene glycol stearyl ether, polyethylene glycol distearyl ether, polyethylene glycol behenyl ether, polyethylene glycol dibehenyl ether, polypropylene glycol methyl ether, polypropylene glycol ethyl ether, polypropylene glycol phenyl ether, polypropylene glycol dimethyl ether, polypropylene glycol diethyl ether, polypropylene glycol diphenyl ether, polypropylene glycol lauryl ether, polypropylene glycol dilauryl ether, polypropylene glycol nonyl ether, polyethylene glycol acetyl ester, polyethylene glycol diacetyl ester, polyethylene glycol benzoic acid ester, polyethylene glycol lauryl ester, polyethylene glycol dilauryl ester, polyethylene glycol nonylic acid ester, polyethylene glycol cetylic acid ester, polyethylene glycol stearoyl ester, polyethylene glycol distearoyl ester, polyethylene glycol behenic acid ester, polyethylene glycol dibehenic acid ester, polypropylene glycol acetyl ester, polypropylene glycol diacetyl ester, polypropylene glycol benzoic acid ester, polypropylene glycol dibenzoic acid ester, polypropylene glycol lauric acid ester, polypropylene glycol dilauric acid ester, polypropylene glycol nonylic acid ester, polyethylene glycol glycerin ether, polypropylene glycol glycerin ether, polyethylene glycol sorbitol ether, polypropylene glycol sorbitol ether, polyethylene glycolated ethylenediamine, polypropylene glycolated ethylenediamine, polyethylene glycolated diethylenetriamine, polypropylene glycolated diethylenetriamine and polyethylene glycolated pentamethylenehexamine.

An amount of the polyethylene glycol-based compound added is preferably from 0.1 to 50% by mass, more preferably from 1 to 30% by mass, based on the total solid content of the image recording layer in view of exerting a sufficiently high solubility inhibiting effect and maintaining good image forming property.

When the above-described measure for enhancing the inhibition (solubility inhibition) is implemented, the sensitivity may decrease. In such a case, addition of a lactone compound is effective. It is believed that when a developer penetrates into the exposed area, the lactone compound reacts with the developer to newly generate a carboxylic acid compound, thereby contributing to dissolution of the exposed area to increase the sensitivity.

The lactone compound is not particularly limited, and examples thereof include the compounds represented by the following formulae (L-I) and (L-II):

In formulae (L-I) and (L-II), X¹, X², X³ and X⁴, which may be the same or different, each represents a constituent atom or atomic group for the ring and each independently may have a substituent, provided that at least one of X¹, X² and X³ in formula (L-I) or at least one of X¹, X², X³ and X⁴ in formula (L-II) has an electron-withdrawing substituent or a substituent substituted by an electron-withdrawing group.

The constituent atom or atomic group for the ring represented by X¹, X², X³ and X⁴ is a nonmetallic atom having two single bonds for forming the ring or an atomic group containing the nonmetallic atom.

The nonmetallic atom or nonmetallic atom group is preferably an atom or atomic group selected from a methylene group, a sulfinyl group, a carbonyl group, a thiocarbonyl group, a sulfonyl group, a sulfur atom, an oxygen atom and a selenium atom, more preferably an atomic group selected from a methylene group, a carbonyl group and a sulfonyl group.

At least one of X¹, X² and X³ in formula (L-I) or at least one of X¹, X², X³ and X⁴ in formula (L-II) has an electron-withdrawing group. The electron-withdrawing group as used in the present invention indicates a group where the Hammett's substituent constant op takes a positive value. The Hammett's substituent constant is described, for example, in Journal of Medicinal Chemistry, Vol. 16, No. 11, 1207-1216 (1973). Examples of the electron-withdrawing group where the Hammett's substituent constant σp takes a positive value include a halogen atom (e.g., fluorine (σp value: 0.06), chlorine (σp value: 0.23), bromine (σp value: 0.23), iodine (σp value: 0.18)), a trihaloalkyl group (e.g., tribromomethyl (σp value: 0.29), trichloromethyl (σp value: 0.33), trifluoromethyl (σp value: 0.54)), a cyano σgroup (σp value: 0.66), a nitro group (op value: 0.78), an aliphatic, aryl or heterocyclic sulfonyl group (e.g., methanesulfonyl (σp value: 0.72)), an aliphatic, aryl or heterocyclic acyl group (e.g., acetyl (σp value: 0.50), benzoyl (σp value: 0.43)), an alkynyl group (e.g., C≡CH (σp value: 0.23)), an aliphatic, aryl or heterocyclic oxycarbonyl group (e.g., methoxycarbonyl (σp value: 0.45), phenoxycarbonyl (σp value: 0.44)), a carbamoyl group (σp value: 0.36), a sulfamoyl group (σp value: 0.57), a sulfoxido group, a heterocyclic group, an oxo group and a phosphoryl group.

The electron-withdrawing group is preferably a group selected from an amido group, an azo group, a nitro group, a fluoroalkyl group having from 1 to 5 carbon atoms, a nitrile group, an alkoxycarbonyl group having from 1 to 5 carbon atoms, an acyl group having from 1 to 5 carbon atoms, an alkylsulfonyl group having from 1 to 9 carbon atoms, an arylsulfonyl group having from 6 to 9 carbon atoms, an alkylsulfinyl group having from 1 to 9 carbon atoms, an arylsulfinyl group having from 6 to 9 carbon atoms, an arylcarbonyl group having from 6 to 9 carbon atoms, a thiocarbonyl group, a fluorine-containing alkyl group having from 1 to 9 carbon atoms, a fluorine-containing aryl group having from 6 to 9 carbon atoms, a fluorine-containing allyl group having from 3 to 9 carbon atoms, an oxo group and a halogen atom.

The electron-withdrawing group is more preferably a group selected from a nitro group, a fluoroalkyl group having from 1 to 5 carbon atoms, a nitrile group, an alkoxycarbonyl group having from 1 to 5 carbon atoms, an acyl group having from 1 to 5 carbon atoms, an arylsulfonyl group having from 6 to 9 carbon atoms, an arylcarbonyl group having from 6 to 9 carbon atoms, an oxo group and a halogen atom.

Specific examples of the compound represented by formulae (L-I) or (L-II) are set forth below, but the present invention is should not be construed as being limited thereto.

An amount of the compound represented by formula (L-I) or (L-II) added is preferably from 0.1 to 50% by mass, more preferably from 1 to 30% by mass, based on the total solid content of the image recording layer. Since the compound reacts with the developer, it is preferred to selectively contact the compound with the developer.

The lactone compounds may be used individually or in combination of two or more thereof. Also, two or more compounds of formula (L-I) or two or more compounds of formula (L-II) may be used in combination at an appropriate ratio to give the total amount thereof in the above-described range.

Also, a thermally decomposable substance, which substantially decreases the solubility of the alkali water-soluble polymer compound before the thermal decomposition, for example, an onium salt, an o-quinonediazide compound, an aromatic sulfone compound or an aromatic sulfonic acid ester compound, is preferably used in combination from the standpoint of enhancing the solubility inhibition of the image area in the developer. Examples of the onium salt include a diazonium salt, an ammonium salt, a phosphonium salt, an iodonium salt, a sulfonium salt, a selenonium salt and an arsonium salt.

Preferable examples of the onium salt for use in the present invention include diazonium salts described in S. I. Schlesinger, Photogr. Sci. Eng., 18, 387 (1974), T. S. Bal et al., Polymer, 21, 423 (1980) and JP-A-5-158230; ammonium salts described in U.S. Pat. Nos. 4,069,055 and 4,069,056 and JP-A-3-140140; phosphonium salts described in D. C. Necker et al., Macromolecules, 17, 2468 (1984), C. S. Wen et al., Teh, Proc. Conf. Rad. Curing ASIA, p. 478, Tokyo (October, 1988), U.S. Pat. Nos. 4,069,055 and 4,069,056; iodonium salts described in J. V. Crivello et al., Macromolecules, 10 (6), 1307 (1977), Chem. & Eng. News, Nov. 28, page 31 (1988), European Patent 104,143, U.S. Pat. Nos. 339,049 and 410,201, JP-A-2-150848 and JP-A-2-296514; sulfonium salts described in J. V Crivello et al., Polymer J., 17, 73 (1985), J. V Crivello et al., J. Org. Chem., 43, 3055 (1978), W. R. Watt et al., J. Polymer Sci., Polymer Chem. Ed., 22, 1789 (1984), J. V Crivello et al., Polymer Bull., 14, 279 (1985), J. V Crivello et al., Macromolecules, 14 (5), 1141 (1981), J. V Crivello et al., J. Polymer Sci., Polymer Chem. Ed., 17, 2877 (1979), European Patents 370,693, 233,567, 297,443 and 297,442, U.S. Pat. Nos. 4,933,377, 3,902,114, 410,201, 339,049, 4,760,013, 4,734,444 and 2,833,827 and German Patents 2,904,626, 3,604,580 and 3,604,581; selenonium salts described in J. V Crivello et al., Macromolecules, 10 (6), 1307 (1977) and J. V Crivello et al., J. Polymer Sci., Polymer Chem. Ed., 17, 1047 (1979); and arsonium salts described in C. S. Wen et al., Teh. Proc. nf. Rad. Curing ASIA, p. 478, Tokyo (October, 1988).

Among the onium salts, diazonium salts are preferred. Particularly preferred examples of the diazonium salt include those described in JP-A-5-158230.

Examples of the counter ion for the onium salt include tetrafluoroboric acid, hexafluorophosphoric acid, triisopropylnaphthalenesulfonic acid, 5-nitro-o-toluenesulfonic acid, 5-sulfosalicylic acid, 2,5-dimethylbenzenesulfonic acid, 2,4,6-trimethylbenzenesulfonic acid, 2-nitrobenzenesulfonic acid, 3-chlorobenzenesulfonic acid, 3-bromobenzenesulfonic acid, 2-fluorocaprylnaphthalenesulfonic acid, dodecylbenzenesulfonic acid, 1-naphthol-5-sulfonic acid, 2-methoxy-4-hydroxy-5-benzoylbenzenesulfonic acid and p-toluenesulfonic acid. Among these, preferred are hexafluorophosphoric acid and an alkyl aromatic sulfonic acid, for example, triisopropylnaphthalenesulfonic acid or 2,5-dimethylbenzenesulfonic acid.

Preferable examples of the quinonediazide include an o-quinonediazide compound. The o-quinonediazide compound for use in the present invention is a compound having at least one o-quinonediazide group and capable of increasing the alkali-solubility through thermal decomposition, and compounds having various structures can be used. Specifically, upon thermal decomposition, the o-quinonediazide loses the ability of inhibiting the dissolution of binder and the o-quinonediazide itself is converted into an alkali-soluble substance. By virtue of these two effects, the solubility of the photosensitive system is improved. Examples of the o-quinonediazide compound usable in the present invention include compounds described in J. Kosar, Light-Sensitive Systems, John Wiley & Sons Inc., pp. 339-352, and in particular, sulfonic acid esters or sulfonic acid amides of o-quinonediazide obtained by reaction with various aromatic polyhydroxy compounds or aromatic amino compounds are preferred. In addition, esters of benzoquinone-(1,2)-diazidesulfonic acid chloride or naphthoquinone-(1,2)-diazide-5-sulfonic acid chloride with pyrogallol-acetone resin described in JP-B-43-28403, and esters of benzoquinone-(1,2)-diazidesulfonic acid chloride or naphthoquinone-(1,2)-diazide-5-sulfonic acid chloride with phenol-formaldehyde resin described in U.S. Pat. Nos. 3,046,120 and 3,188,210 may also be preferably used.

Furthermore, esters of naphthoquinone-(1,2)-diazide-4-sulfonic acid chloride with phenol-formaldehyde resin or cresol-formaldehyde resin, and esters of naphthoquinone-(1,2)-diazide-4-sulfonic acid chloride with pyrogallol-acetone resin may also be preferably used. Other useful examples of the o-quinonediazide compound include those described in a large number of patents, for example, JP-A-47-5303, JP-A-48-63802, JP-A-48-63803, JP-A-48-96575, JP-A-49-38701 and JP-A-48-13354, JP-B-41-11222, JP-B-45-9610, JP-B-49-17481, U.S. Pat. Nos. 2,797,213, 3,454,400, 3,544,323, 3,573,917, 3,674,495 and 3,785,825, British Patents 1,227,602, 1,251,345, 1,267,005, 1,329,888 and 1,330,932 and German Patent 854,890.

An amount of the o-quinonediazide compound added is preferably from 1 to 50% by mass, more preferably from 5 to 30% by mass, still more preferably from 10 to 30% by mass, based on the total solid content of the image recording layer. The o-quinonediazide compounds may be used individually or as a mixture of two or more thereof.

Also, at least partially esterified alkali-soluble resin described in JP-A-11-288089 may be contained.

Furthermore, for the purpose of enhancing the dissolution inhibiting property of the image recording layer and elevating the resistance against scratch on the surface thereof, it is preferred to use in combination a polymer comprising as a polymerization component, a (meth)acrylate monomer containing two or three perfluoroalkyl groups having from 3 to 20 carbon atoms in its molecule described in JP-A-2000-187318. An amount of the polymer added is preferably from 0.1 to 10% by mass, more preferably from 0.5 to 5% by mass, based on the total solid content of the image recording layer.

-Development Accelerator-

In order to more increase the sensitivity, an acid anhydride, a phenol or an organic acid may also be used in combination.

The acid anhydride is preferably a cyclic acid anhydride, and specific examples of the cyclic acid anhydride which can be used include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, 3,6-endooxy-tetrahydrophthalic anhydride, tetrachlorophthalic anhydride, maleic anhydride, chloromaleic anhydride, α-phenylmaleic anhydride, succinic anhydride and pyromellitic anhydride described in U.S. Pat. No. 4,115,128. Examples of a non-cyclic acid anhydride includes acetic anhydride.

Examples of the phenol include bisphenol A, 2,2′-bishydroxysulfone, p-nitrophenol, p-ethoxyphenol, 2,4,4′-trihydroxybenzophenone, 2,3,4-trihydroxybenzophenone, 4-hydroxybenzophenone, 4,4′,4″-trihydroxytriphenylmethane and 4,4′,3″,4″-tetrahydroxy-3,5,3′,5′-tetramethyltriphenylmethane.

Examples of the organic acid include a sulfonic acid, a sulfinic acid, an alkylsulfuric acid, a phosphonic acid, a phosphoric acid ester and a carboxylic acid described in JP-A-60-88942 and JP-A-2-96755. Specific examples thereof include p-toluenesulfonic acid, dodecylbenzenesulfonic acid, p-toluenesulfinic acid, ethylsulfuric acid, phenylphosphonic acid, phenylphosphinic acid, phenyl phosphate, diphenyl phosphate, benzoic acid, isophthalic acid, adipic acid, p-toluic acid, 3,4-dimethoxybenzoic acid, phthalic acid, terephthalic acid, 4-cyclohexene-1,2-dicarboxylic acid, erucic acid, lauric acid, n-undecanoic acid and ascorbic acid.

A content of the acid anhydride, phenol and organic acid in the image recording layer is preferably from 0.05 to 20% by mass, more preferably from 0.1 to 15% by mass, still more preferably from 0.1 to 10% by mass.

-Surfactant-

To the heat-sensitive layer, nonionic surfactants described in JP-A-62-251740 and JP-A-3-208514, amphoteric surfactants described in JP-A-59-121044 and JP-A-4-13149, siloxane-based compounds described in EP-950517, or copolymers of fluorine-containing monomer described in JP-A-62-170950, JP-A-11-288093 and Japanese Patent Application No. 2001-247351 may be added in order to improve coating property and to increase stability of processing according to development conditions.

Specific examples of the nonionic surfactant include sorbitan tristearate, sorbitan monopalmitate, sorbitan trioleate, stearic acid monoglyceride and polyoxyethylene nonyl phenyl ether. Specific examples of the amphoteric surfactant include alkyldi(aminoethyl)glycine, alkylpolyaminoethylglycine hydrochloride, 2-alkyl-N-carboxyethyl-N-hydroxyethylimidazolinium betaine and N-tetradecyl-N,N-betaine type surfactant (for example, “Amorgen K” (trade name) produced by Dai-Ichi Kogyo Seiyaku Co., Ltd.).

The siloxane-based compound is preferably a block copolymer of dimethylsiloxane and polyalkylene oxide, and specific examples thereof include a polyalkylene oxide-modified silicone, for example, DBE-224, DBE-621, DBE-712, DBP-732 or DBP-534 produced by Chisso Corp. and Tego Glide 100 produced by Tego in Germany.

A content of the nonionic or amphoteric surfactant is preferably from 0.01 to 15% by mass, more preferably from 0.1 to 5% by mass, still more preferably from 0.05 to 0.5% by mass, based on the total solid content of the image recording layer.

-Printing Out Agent/Coloring Agent-

To the printing plate material, a printing out agent for obtaining a visible image immediately after heating upon exposure, or a dye or pigment as an image coloring agent can be added.

A representative example of the printing out agent is a combination of a compound (photo acid releaser) capable of releasing an acid with heating upon exposure with an organic dye capable of forming a salt. Specific examples thereof include a combination of a o-naphthoquinonediazide-4-sulfonic acid halogenide with a salt-forming organic dye described in JP-A-50-36209 and JP-A-53-8128, and a combination of a trihalomethyl compound with a salt-forming organic dye described in JP-A-53-36223, JP-A-54-74728, JP-A-60-3626, JP-A-61-143748, JP-A-61-151644 and JP-A-63-58440. The trihalomethyl compound includes an oxazole-based compound and a triazine-based compound, which are both excellent in preservation stability and provide a clear print-out image.

As for the image coloring agent, dyes other than the above-described salt-forming organic dyes may also be used. Preferable dyes include oil-soluble dyes and basic dyes, including the salt-forming organic dyes. Specific examples thereof include Oil Yellow #101, Oil Yellow #103, Oil Pink #312, Oil Green BG, Oil Blue BOS, Oil Blue #603, Oil Black BY, Oil Black BS, Oil Black T-505 (produced by Orient Kagaku Kogyo Co., Ltd.), Victoria Pure Blue, Crystal Violet Lactone, Crystal Violet (CI 42555), Methyl Violet (CI 42535), Ethyl Violet, Rhodamine B (CI 45170B), Malachite Green (CI 42000) and Methylene Blue (CI 52015). Dyes described in JP-A-62-293247 are particularly preferred.

Such a dye can be added in an amount of 0.01 to 10% by mass, preferably from 0.1 to 3% by mass, based on the total solid content of the image recording layer.

-Plasticizer-

To the printing plate material, a plasticizer is further added, if desired, in order to impart flexibility or the like to the coated film. Examples of the plasticizer include butyl phthalyl, polyethylene glycol, tributyl citrate, diethyl phthalate, dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, tricresyl phosphate, tributyl phosphate, trioctyl phosphate, tetrahydrofurfuryl oleate and an oligomer or polymer of acrylic acid or methacrylic acid.

-Wax Agent-

To the image recording layer of the photosensitive lithographic printing plate precursor, a compound capable of decreasing a coefficient of static friction on the surface thereof may be added for the purpose of imparting resistance against scratch. Specific examples of the compound include compounds having an ester of long-chain alkylcarboxylic acid described in U.S. Pat. No. 6,117,913 and Japanese Patent Application Nos. 2001-261627, 2002-32904 and 2002-165584. An amount of the compound added is preferably from 0.1 to 10% by mass, more preferably from 0.5 to 5% by mass, based on the total solid content constituting the layer.

The photosensitive lithographic printing plate precursor can be ordinarily produced by dissolving a photo-sensitive layer (heat-sensitive layer) composition containing the above-described components in a solvent and coating the resulting solution on an appropriate support.

[Coating Solvent]

Examples of the solvent used include ethylene dichloride, cyclohexanone, methyl ethyl ketone, methanol, ethanol, propanol, ethylene glycol monomethyl ether, 1-methoxy-2-propanol, 2-methoxyethyl acetate, 1-methoxy-2-propyl acetate, dimethoxyethane, methyl lactate, ethyl lactate, N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, tetramethylurea, N-methylpyrrolidone, dimethyl sulfoxide, sulfolane, γ-butyrolactone, toluene and water, but the present invention should not be construed as being limited thereto. The solvents are used individually or as a mixture.

With respect to selection of the coating solvent, in the case where the photosensitive lithographic printing plate precursor has a two-layer structure of an upper recording layer and a lower recording layer, the coating solvent for the upper recording layer is preferably selected from those of substantially not dissolving the lower recording layer, in order to prevent compatibility at the interface of these layers adjacently provided. The concentration of the above-described components (total solid content including additives) in the solvent is preferably from 1 to 50% by mass.

In the case of using an acid anhydride, a content of water in the coating solution is preferably controlled to 0.5% or less.

[Coated Amount]

A coated amount (solid content) of the heat-sensitive composition varies depending on use but in view of film properties and press life, the composition can be provided in a coated amount of 0.3 to 3.0 g/m², preferably from 0.5 to 2.5 g/m², more preferably from 0.8 to 1.6 g/m².

[Multilayer Structure]

In the photosensitive lithographic printing plate precursor for use in the present invention, an image recording layer containing the above-described components is provided on a support. The image recording layer may have a multilayer structure of two or more layers. For the sake of convenience, the case having a two-layer structure consisting of an upper side layer and a lower side layer is described below.

In the case, an alkali-soluble resin constituting the upper side layer and the lower side layer may be the alkali-soluble resin described above, but the alkali-soluble resin used for the upper side layer preferably has a lower solubility in alkali than that of the lower side layer.

The infrared absorbing dye used may be different in the respective layers, or a plurality of infrared absorbing dyes may be used in the respective layers. As described above, the dye can be added in an amount of 0.01 to 50% by mass, preferably from 0.1 to 50% by mass, more preferably from 0.1 to 30% by mass, based on the total solid content of the layer to which the dye is added. In the case of adding the dye to a plurality of layers, it is preferred that the total amount of the dye added falls within the range described above.

Since the above-described thermally decomposable substance, which substantially decreases the solubility of the alkali-soluble resin before the thermal decomposition, may partially decompose with the lapse of time, in the case of the image recording layer having a multilayer structure, it may be effective to incorporate the substance into the lower side layer, but the substance can be added in either layer or in both layers. The amount of the substance added is as described above. In the case of adding the substance to a plurality of layers, it is preferred that the total amount of the substance added falls within the range described above.

The lactone compound may be added in either layer or in both layers, though in the case of a multilayer structure, it is effective to incorporate the lactone compound into the upper side layer.

[Support]

A hydrophilic support for use in the photosensitive lithographic printing plate precursor includes a dimensionally stable plate-like material with necessary strength and durability. Examples thereof include paper, paper laminated with plastic (e.g., polyethylene, polypropylene or polystyrene), a metal plate (e.g., aluminum, zinc or copper), a plastic film (e.g., cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate or polyvinyl acetal), and paper or a plastic film laminated or vapor-deposited with the above-described metal.

Among the supports, a polyester film and an aluminum plate are preferred, and the aluminum plate is more preferred because it is dimensionally stable and relatively inexpensive. The aluminum plate is preferably a pure aluminum plate or an alloy plate containing mainly aluminum and a trace amount of hetero element. A plastic film laminated or vapor-deposited with aluminum may also be used. Examples of the hetero element contained in the aluminum alloy include silicon, iron, manganese, copper, magnesium, chromium, zinc, bismuth, nickel and titanium. The content thereof in the alloy is at most 10% by mass or less.

The particularly preferred aluminum plate is a pure aluminum plate, but a completely pure aluminum plate is difficult to produce in view of refining technique and therefore, an aluminum plate containing trace hetero elements may be used. Such an aluminum plate is not particularly limited in its composition, and a conventionally known and used material can be appropriately used. A thickness of the aluminum plate for use in the present invention is approximately from 0.1 to 0.6 mm, preferably from 0.15 to 0.4 mm, more preferably from 0.2 to 0.3 mm.

In advance of surface-roughening the aluminum plate, a degreasing treatment for removing a rolling oil on the surface thereof is performed, if desired, using a surfactant, an organic solvent, an alkaline aqueous solution or the like. A surface-roughening treatment of the aluminum plate surface is performed by various methods, for example, a mechanical surface-roughening method, a surface-roughening method of electrochemically dissolving the surface or a surface-roughening method of chemically dissolving the surface selectively. As for the mechanical method, a known method, for example, ball graining, brush graining, blast graining and buff graining may be used. As for the electrochemical surface-roughening method, a method of passing an alternating or direct current in an electrolytic solution of hydrochloric acid or nitric acid may be used. Also, a method using these two methods in combination described in JP-A-54-63902 may be employed.

The surface-roughened aluminum plate is subjected to an alkali etching treatment and a neutralization treatment, if desired, and then subjected to an anodizing treatment, if desired, in order to enhance water retentivity and abrasion resistance of the surface. As for an electrolyte used in the anodizing treatment of aluminum plate, various electrolytes capable of forming a porous oxide film may be used. Ordinarily, sulfuric acid, phosphoric acid, oxalic acid, chromic acid or a mixed acid thereof is used. A concentration of the electrolyte is appropriately determined according to the kind of electrolyte.

Since the anodizing treatment conditions vary depending on the electrolyte used, they cannot be indiscriminately specified. Ordinarily, however, the conditions are suitably such that the concentration of electrolyte is from 1 to 80% by mass, the liquid temperature is from 5 to 70° C., the current density is from 5 to 60 A/dm², the voltage is from 1 to 100 V, and the electrolysis time is from 10 seconds to 5 minutes. The amount of the anodic oxide film formed is preferably 1.0 g/m² or more in view of press life. After the anodizing treatment, the aluminum surface is subjected to a hydrophilization treatment, if desired. The hydrophilization treatment includes an alkali metal silicate (for example, aqueous sodium silicate solution) method described in U.S. Pat. Nos. 2,714,066, 3,181,461, 3,280,734 and 3,902,734. According to the method, the support is dipped or electrolyzed in an aqueous sodium silicate solution. Other examples include a method of treating the support with potassium fluorozirconate described in JP-B-36-22063 or with polyvinylphosphonic acid described in U.S. Pat. Nos. 3,276,868, 4,153,461 and 4,689,272.

The photosensitive lithographic printing plate precursor for use in the present invention comprises at least the above-described image recording layer provided on a support, but if desired, an undercoat layer may be provided between the support and the image recording layer.

As for a component of the undercoat layer, various organic compounds are used, which are selected from, for instance, carboxymethyl cellulose; dextrin; gum arabic; an amino group-containing phosphonic acid, for example, 2-aminoethylphosphonic acid; an organic phosphonic acid, which may have a substituent, for example, phenylphosphonic acid, naphthylphosphonic acid, alkylphosphonic acid, glycerophosphonic acid, methylenediphosphonic acid or ethylenediphosphonic acid; an organic phosphoric acid, which may have a substituent, for example, phenylphosphoric acid, naphthylphosphoric acid, alkylphosphoric acid or glycerophosphoric acid; an organic phosphinic acid, which may have a substituent, for example, phenylphosphinic acid, naphthylphosphinic acid, alkylphosphinic acid or glycerophosphinic acid; an amino acid, for example, glycine and β-alanine; and a hydrochlorides of hydroxy group-containing amine, for example, hydrochloride of triethanolamine. The organic compounds may be used as a mixture of two or more thereof.

Also, an undercoat layer containing at least one compound selected from organic polymer compounds having a structural unit represented by the following formula is preferred.

wherein R¹¹ represents a hydrogen atom, a halogen atom or an alkyl group, R¹² and R¹³ each independently represents a hydrogen atom, a hydroxy group, a halogen atom, an alkyl group, a substituted alkyl group, an aryl group, a substituted aryl group, —OR¹⁴, —COOR¹⁵, —CONHR¹⁶, —COR¹⁷ or —CN, or R¹² and R¹³ may be combined with each other to form a ring, R¹⁴ to R¹⁷ each independently represents an alkyl group or an aryl group, X represents a hydrogen atom, a metal atom or NR¹⁸R¹⁹R²⁰R²¹, R¹⁸ to R²¹ each independently represents a hydrogen atom, an alkyl group, a substituted alkyl group, an aryl group or a substituted aryl group, or R¹⁸ and R¹⁹ may be combined with each other to form a ring, and m represents an integer of 1 to 3.

The undercoat layer can be provided by the following method. Specifically, the undercoat layer can be provided by a method where the organic compound is dissolved in water, an organic solvent, for example, methanol, ethanol or methyl ethyl ketone, or a mixed solvent thereof and the resulting solution is coated on an aluminum plate and then dried, or a method where an aluminum plate is dipped in a solution resulting from dissolving the organic compound in water, an organic solvent, for example, methanol, ethanol or methyl ethyl ketone, or a mixed solvent thereof to adsorb the compound, then washed with water or the like and dried. In the former method, a solution containing the organic compound at a concentration of 0.005 to 10% by mass can be coated by various methods. In the latter method, the concentration of the solution is from 0.01 to 20% by mass, preferably from 0.05 to 5% by mass, the dipping temperature is from 20 to 90° C., preferably from 25 to 50° C., and the dipping time is from 0.1 second to 20 minutes, preferably from 2 seconds to 1 minute. The solution used therefor may be adjusted to a pH of 1 to 12 using a basic substance, for example, ammonia, triethylamine or potassium hydroxide, or an acidic substance, for example, hydrochloric acid or phosphoric acid.

A coverage of the undercoat layer is suitably from 2 to 200 mg/m², preferably from 5 to 100 mg/m² in view of press life.

The photosensitive lithographic printing plate precursor thus-prepared is imagewise exposed and then subjected to development processing using an alkali developing solution which is described in detail above.

Examples of a light source for actinic ray used for the imagewise exposure include a mercury lamp, a metal halide lamp, a xenon lamp, a chemical lamp and a carbon arc lamp. Examples of radiation for the imagewise exposure include electron beam, X-ray, ion beam and far infrared ray. Also, g-line, i-line, Deep-UV light and high-density energy beam (laser beam) may be used. Examples of the laser beam include helium-neon laser, argon laser, krypton laser, helium-cadmium laser and KrF excimer laser. In the present invention, a light source having a light emission wavelength in the region from near infrared to infrared is preferred, and a solid laser and a semiconductor laser are more preferred.

In the case where an unnecessary image portion is present on the lithographic printing plate obtained through the imagewise exposure, development, and water washing and/or rinsing and/or gumming, the unnecessary image portion is erased. The erasure is preferably performed by a method described in JP-B-2-13293, where an erasing solution is coated on the unnecessary image portion, the plate is allowed to stand as it is for a predetermined time and then washed with water, but may also be performed by a method described in JP-A-59-174842, where the unnecessary image portion is irradiated with active ray guided by an optical fiber and then developed.

The lithographic printing plate obtained according to the above is coated with a desensitizing gum, if desired, and then can be used for printing, but in the case of imparting more improved press life to the lithographic printing plate, a burning treatment is applied thereto. In performing the burning treatment, the lithographic printing plate before the burning is preferably treated with a surface-conditioning solution described in JP-B-61-2518, JP-B-55-28062, JP-A-1-31859 and JP-A-61-159655.

With respect to the method therefor, the surface-conditioning solution is coated on the lithographic printing plate using a sponge or absorbent cotton impregnated with the solution or by dipping the printing plate in a vat filled with a surface-conditioning solution, or the surface-conditioning solution is coated by an automatic coater. To uniform the coated amount using a squeegee after coating or a squeegee roller provides more advantageous results.

A coated amount of the surface-conditioning solution is ordinarily from 0.03 to 0.8 g/m² (dry weight). The lithographic printing plate coated with the surface-conditioning solution is dried, if desired, and then heated at a high temperature using a burning processor (for example, Burning Processor BP-1300 available from Fuji Photo Film Co., Ltd.). In such a case, though the heating temperature and heating time vary depending on the kind of components constituting the image, they are preferably from 180 to 300° C. and from 1 to 20 minutes, respectively.

The lithographic printing plate after the burning treatment may be appropriately subjected to, if desired, conventional treatments, for example, water washing or gumming. However, when the surface-conditioning solution used contains a water-soluble polymer compound or the like, a so-called desensitizing treatment, for example, gumming can be omitted. The lithographic printing plate obtained through such treatments is mounted on an offset printing press and then used for printing a large number of sheets.

The automatic developing machine of present invention is described below.

FIG. 1 is a constitutional view showing a first embodiment of an automatic developing machine used for practicing the development replenisher replenishment method according to the present invention. As shown in FIG. 1, the automatic developing machine 2 comprises a developing unit 6 for developing a photosensitive lithographic printing plate precursor (hereinafter referred to as a “PS plate”) 4, an after-processing unit 8 for washing off the developer adhered to the developed PS plate 4 and also for coating a gum solution thereon, and a drying unit 10 for drying the PS plate coated with the gum solution.

In the case of processing a PS plate, which requires heating prior to the development processing, a preheating unit (not shown in FIG. 1) may be provided. The preheating unit is disposed on the upstream side of the developing unit 6 in the transport direction and has a function of keeping a predetermined PS plate surface temperature for a predetermined period of time as the PS plate is transported. The PS plate inserted into the preheating unit is automatically transported to the next step while being heated. The developing apparatus may also comprise a pre-washing unit (not shown in FIG. 1). The pre-washing unit is disposed on the upstream side of the developing unit 6 in the transport direction and on the downstream side of the preheating unit in the transport direction and has a function of washing and cooling the PS plate surface with washing water as the PS plate is transported. The PS plate inserted into the pre-washing unit is automatically transported to the next step, that is, the developing unit 6.

An insert port 14 is formed in a side board 12 of the automatic developing machine 2, and the PS plate 4 inserted from the insert port 14 is transported to the developing unit 6 by transport rollers 16. At the insert port 14, a rubber blade 18 is provided and when the PS plate 4 is not inserted, the insert port 14 is closed by the rubber blade 18.

In a developing tank 20 of the developing unit 6, transport rollers 22, brush rollers 24 and squeeze rollers 26 are sequentially provided from the upstream side in the transport direction, and backup rollers 28 are also provided at appropriate positions between those rollers. As the plate is transported by the transport rollers 22, the PS plate 4 is dipped in the developer to conduct development processing.

The after-processing unit 8 connecting to the developing unit 6 comprises a washing unit 8 a and a finisher unit 8 b. In the washing unit 8 a, rollers 30 a′ and 30 a for transporting the PS plate 4, a washing tank 32 a and nozzle members 34 a for spraying washing water in the washing tank 32 a to the PS plate 4 are provided. Also, a washing water supply pump 78 a for supplying the washing water to the washing tank 32 a is provided. In the finisher unit 8 b, rollers 30 b for transporting the PS plate 4, a finisher tank 32 b, and nozzle members 34 b for spraying the finisher solution in the finisher tank 32 b to the PS plate 4 are provided. Also, a gum solution supply pump 77 for supplying the gum solution to the finisher tank 32 b, and a gum solution diluent supply pump 78 b for supplying a gum solution diluent are provided. The developed PS plate 4 is washed with a washing water sprayed from the ejection member 34 a as it is transported by the transport rollers 30 a, and thereafter coated with a finisher solution sprayed from the ejection member 34 b as the PS plate 4 is transported by transport rollers 30 b.

At this time, the diluent 57 in the replenisher diluent tank 53 is replenished to the washing tank 32 a by the washing water supply pump 78 a. In the finisher tank 32 b, the gum solution in the gum solution tank 56 is replenished by the pump 77 and at the same time, the diluent 57 in the replenisher diluent storage tank 53 is replenished by the replenisher diluent supply pump 78 b. The replenishment ratio between the gum solution and the diluent is, for example, 1:1. Along with such replenishment, a washing solution overflowed from the washing tank 32 a and a gum waste solution overflowed from the finisher tank 32 b are recovered in a waste solution tank 54 similarly to a development waste solution.

It is also effective to provide a washing brush roller (not shown in FIG. 1) in the washing unit 8 a. The washing brush roller is disposed between the nozzle member 34 a and the PS plate 4 to abut on the top surface or top and bottom surfaces of the PS plate 4, and while rotating, rubs to wash the surface of PS plate 4 under transportation.

On the other hand, a structure where the washing part 8 a works as a first finisher unit 8 a and the finisher unit 8 b works as the second finisher unit 8 b is also effective. In the first finisher unit 8 a and second finisher unit 8 b, transport rollers 30 a and 30 b for transporting the PS plate 4 and nozzle members 34 a and 34 b for spraying the gum solution in finisher tanks 32 a and 32 b to the PS plate 4 are provided. The PS plate 4 after the development is coated with the gum solution sprayed by the nozzle members 34 a and 34 b as it is transported by the transport rollers 30 a and 30 b. At this time, the gum solution in the finisher tank 32 b of the second finisher unit 8 b located on the downstream side is overflowed to be supplied to the finisher tank 32 a of the first finisher unit 8 a located on the upstream side, but in stead of such a constitution, the gum solution may be similarly supplied using a pump or the like. In this case, the washing water supply pump 78 a is not used.

In the second finisher tank 32 b, the gum solution in the gum solution tank 56 is replenished by the pump 77 and at the same time, the diluent 57 in the replenisher diluent storage tank 53 is replenished by the replenisher diluent supply pump 78. The replenishment ratio between the gum solution and the diluent is, for example, 1:1. Along with such replenishment, a gum waste solution overflowed from the first finisher tank 32 a is recovered in the waste solution tank 54 similarly to the development waste solution.

In the drying unit 10 connecting to the finisher unit 8, a guide roller 36 and a pair of skewer rollers 38 are sequentially provided from the upstream side in the transport direction. Also, in the drying unit 10, a drying means (not shown), for example, a warm-air supply means or a heat-generating means is provided. A discharge port 40 is provided in the drying unit 10 and the PS plate 4 dried by the drying means is discharged from the discharge port 40. Furthermore, a shutter 44 is provided in a passage between the drying unit 10 and the finisher unit 8 and when the PS plate 4 is not passing through the passage 46, the passage 46 is closed by the shutter 44.

In a developing tank 20, a box-shaped shielding cover 60 is provided integrally with a tank wall. A bottom wall of the shielding cover 60 is structured to have curved depressions so as not to contact with upper circumferential surfaces of the transport roller 22, brush roller 24 and backup roller 28, thereby preventing from interference with rollers or the like. By virtue of the box shape of the shielding cover 60, an airtight space is formed above the developing tank 20 to provide an effect of minimizing an amount of air in the developing unit 6. Moreover, owing to the presence of the shielding cover 60, an area of the developer contacting with air is made as small as possible.

In the automatic developing apparatus 2 having the above-described construction, rubber blades 62 are provided at appropriate positions to construct a substantially airtight space from the developing unit 6 to the finisher unit 8 b, whereby external air is prevented from flowing into the developing unit 6. The space between the developing unit 6 and the washing unit 8 a is also made substantially airtight by a rubber blade 62 and the air in the washing unit 8 a is prevented from flowing into the developing unit 6. Accordingly, the developing unit 6 is substantially airtight and established to have a closed construction allowing for almost no inflow of air, although air slightly flows into the developing unit 6 at the passage of PS plate 4.

The developing unit 6 is described in detail below. The developing tank 20 is connected to a circulation pipe 80 for the developer. In the circulation pipe 80, a developer circulation pump 71, an electric conductivity sensor 73 and a filter (not shown) are provided. The developer in the developing tank 20 is sucked into the circulation pipe 80 by the developer circulation pump 71 through the suction hole provided in the bottom of the developing tank 20, circulated in the circulation pipe 80 and discharged again into the developing tank 20. The filter filters the developer flowing in the circulation pipe 80. The electric conductivity sensor 73 as an electric conductivity measuring unit measures the electric conductivity of the developer flowing in the circulation pipe 80.

Also, in the developing unit 6, members constituting a replenishment device, specifically, replenisher pipes 90 and 91, a replenisher stock solution storage tank 55 connected to the replenisher pipe 90, a replenisher stock solution supply pump 74 intervened in the replenisher pipe 90, a replenisher diluent storage tank 53 connected to the replenisher pipe 91, and a replenisher diluent supply pump 76 intervened in the replenisher pipe 91, are provided and these function as replenisher supply means. The development waste solution overflowed from the developing tank 20 is recovered in the waste solution tank 54.

More specifically, a pair of replenisher pipes 90 and 91 for the development replenisher obtained by diluting the development replenisher stock solution 58 with the replenisher diluent 57 is provided in the vicinity of the developing tank 20. The replenisher pipe 90 for the development replenisher stock solution 58 is connected to the replenisher stock solution storage tank 55 at another end (bottom in FIG. 1), and in the pipe, the replenisher stock solution supply pump 74 is provided. The replenisher stock solution supply pump 74 supplies the development replenisher stock solution 58 to the developing tank 20 from the replenisher stock solution storage tank 55. The replenisher pipe 91 for the replenisher diluent 57 is connected to the replenisher diluent storage tank 53 at another end (bottom in FIG. 1), and in the pipe, the replenisher diluent supply pump 76 is provided. The replenisher diluent supply pump 76 supplies the replenisher diluent (water) 57 to the developing tank 20 from the replenisher diluent storage tank 53. In other words, a diluent replenishment device is constituted by the replenisher pipe 91, the replenisher diluent supply pump 76 and the replenisher diluent storage tank 53.

The replenisher stock solution supply pump 74 and the replenisher diluent supply pump 76 are controlled by a controlling device (controlling means) 50 comprising a controlling ROM 51 a or controlling RAM 51 b as a condition memorizing device and a time measuring unit 52, based on signals from the electric conductivity sensor 73 and the time measuring unit 52. Also, the controlling device 50 processes the transportation of PS plates by driving the transport rollers 22, brush rollers 24, squeeze rollers 26 and the like at appropriate timing based on signals from the plate detection sensor 27.

Further, the controlling device 50 uses the time measuring unit 52 to measure the time elapsed from the last replenishment, calculates the area of the printing plate precursor according to the signal from the plate detecting sensor 27 and then uses the electric conductivity sensor 73 to measure the electric conductivity of the developer. The controlling device 50 then utilizes these values to supply a development replenisher (development replenisher stock solution 58 plus replenishment diluent 57) into the developing tank 20 from the replenisher stock solution storage tank 55 and the replenishment diluent storage tank 53 at predetermined replenishment rate and percent replenisher dilution as necessary.

The control by the controlling device 50 will be described hereinafter. FIGS. 2 to 12 each depict an example of flow chart indicating the controlling method by the controlling device 50. Generally speaking, in the basic controlling method (first controlling system) of the invention shown in FIG. 2, the amounts of the time lapse replenisher/processing replenisher required to keep the developer activity constant are calculated according to time lapse replenishment rate/processing replenishment rate which have been predetermined to certain provisional values. The calculated value of electric conductivity determined from these values and the electric conductivity of developer measured at a predetermined time interval are then compared to increase or decrease the predetermined time lapse replenishment rate/predetermined processing replenishment rate to modified values according to which necessary time lapse/processing replenishment rate is provided. In this manner, even when processing conditions such as kind and size of printing plate and frequency of processing and atmospheric conditions such as atmospheric carbon dioxide gas concentration and humidity are varied, replenishment can be effected according to proper amounts of time lapse replenisher and processing replenisher.

Firstly, a first controlling shown in FIG. 2 will be described.

At Step 1 (hereinafter referred to as “S1”), if a predetermined period of time has been elapsed, the replenisher is replenished in an amount of a time lapse replenisher calculated from a predetermined value of time lapse replenishment rate and elapsed time. Subsequently, at S2, if the printing plate precursor has been processed at a predetermined time interval, the replenisher is replenished in an amount of a time processing replenishment rate calculated from a predetermined value of processing replenishment rate and processed area.

Subsequently, at S3, if the predetermined value R of replenishment system is a value indicating an electric conductivity-based replenishment system: 1, the processing proceeds to S4. If not, the processing proceeds to S10. Referring to the predetermined value R of replenishment system, an electric conductivity-based replenishment system is set in an ordinary operation. However, when the electric conductivity sensor 73 is out of order or in like states, this electric conductivity-based replenishment system does not function normally. In this case, the predetermined value R of replenishment system is changed to a value other than 1.

The change of the predetermined value R of replenishment system may be effected automatically or manually. In order to automatically change the predetermined value R of replenishment system, the output value of the electric conductivity sensor 73 is compared with a predetermined range. If the output value of the electric conductivity sensor 73 exceeds the predetermined range, it is considered that the electric conductivity sensor 73 is out of order. Then, the predetermined value R of replenishment system is automatically changed to a value other than 1. The method of judging to see if the electric conductivity sensor 73 is out of order is not limited to the aforementioned method. For example, the judgment can be carried out by examining the external appearance of the probe portion of the electric conductivity sensor 73 to see if it is stained.

On the other hand, in order to manually change the predetermined value R of replenishment system, when a phenomenon is visually observed on the printing plate precursor thus processed such as phenomenon that the photosensitive layer on the image area is excessively developed and dissolved to reduce the thickness thereof, phenomenon that the image area which is supposed to form a dot image is developed and dissolved away and phenomenon that the photosensitive layer on the nonimage area is left undissolved, it is considered that the electric conductivity sensor 73 is out of order to cause failure in the electric conductivity-based replenishment system. Then, the predetermined value R of replenishment system is changed to a value other than 1.

Accordingly, at S3, distinction is made between the case where the electric conductivity sensor 73 is being normally operated and the case where the electric conductivity sensor 73 is in other states such as failure. Different processing is made from one of the two cases to the other. In some detail, in the former case of normal operation, the operation is effected on an electric conductivity basis. In the latter case, the operation is effected, e.g., on an area and time lapse basis involving no use of measured value of electric conductivity. In this manner, the operation of the automatic developing machine can be continued on a developer replenishment basis involving no electric conductivity during failure of the electric conductivity sensor 73 or in other occasions, making it possible to continue the operation of the apparatus without fully suspending the operation of the apparatus until the maintenance operator is called.

At S4, it is judged to see if the time which has been elapsed since the starting time or the last time at which the electric conductivity of developer has been measured reaches a predetermined time. If so, the processing proceeds to S5. If not, the processing proceeds to S10.

At S5, the electric conductivity of the developer is measured. Subsequently, at S6, the calculated value of electric conductivity is calculated from the replenished amounts of time lapse replenisher/processing replenisher.

At S7, the calculated value of electric conductivity and the aforementioned measured value of electric conductivity are compared. If the measured value of electric conductivity is greater than the calculated value of electric conductivity, the processing proceeds to S8. If the measured value of electric conductivity is smaller than the calculated value of electric conductivity, the processing proceeds to S9.

At S8, both the processing replenishment rate and the time lapse replenishment rate are decreased by a predetermined amount. On the other hand, at S9, both the processing replenishment rate and the time lapse replenishment rate are increased by a predetermined amount.

At S10, the state of the operation switch of the automatic developing machine is examined. If the operation switch has been ON, the processing proceeds to S1. If the operation switch has been OFF, the operation of the automatic developing machine is suspended to finish the processing.

A second controlling will be described hereinafter in connection with FIGS. 3 and 4.

At S11, integrated value of time lapse replenishment rate (I_(VC)) and integrated value of processing replenishment rate (I_(VB)), which are variables used during controlling, are initialized. In other words, 0 is substituted in I_(VC) and I_(VB). Further, it is judged to see if the operation of the automatic developing machine is started for the first time. If so, the percent replenisher replacement (X) and the percent time lapse replenishment (F), which are variables used during controlling, are initialized. In some detail, 0 is substituted in X and C₅ is substituted in F.

At S12, it is judged to see if the time elapsed from starting or the last time at which the time lapse replenishment rate has been integrated reaches a predetermined time T_(K). If so, the processing proceeds to S13. If not, the processing proceeds to S14. At S13, the amount of the time lapse replenisher required at elapsed time T_(K) is calculated from predetermined value of time lapse replenishment rate V_(C) and then integrated to I_(VC). For example, the calculation is made as follows. I _(VC) +V _(C) ×T _(K) →I _(VC)  (9)

At S14, it is judged to see if the area which has been processed since the starting time or the last time at which the processing replenishment rate has been integrated reaches a predetermined processed area S. If so, the processing proceeds to S15. If not, the processing proceeds to S16. At S15, the amount of the processing replenisher required for processed area S is calculated from the predetermined value V_(B) of processing replenishment rate and then integrated to I_(VB). For example, the calculation is made as follows. I _(VB) +V _(B) ×S→I _(VB)  (10)

Subsequently, at S16, it is judged to see if the time which has been elapsed since the starting time or the last time at which the electric conductivity of developer has been measured reaches a predetermined time T_(D). If so, the processing proceeds to S17. If not, the processing proceeds to S33.

At S17, the electric conductivity of the developer is measured. The measured value is then substituted in variable d_(M). Subsequently, at S18, the time T_(P) elapsed from the last time at which replenishment is effected is measured. Subsequently, at S19, the calculated value d_(T1) of electric conductivity 1 is calculated from the percent replenisher replacement X, and the percent time replenishment F using a predetermined calculation formula. As the calculation formula there may be used the following formula (11). d _(T1)=(1−X)×D _(M) +X×[(1−F)×D _(B) +F×D _(C)]  (11) (D_(M), D_(C) and D_(B) are preliminary experimentally obtained constants.)

Subsequently, at S20, the calculated value d_(T2) of electric conductivity 2 is calculated from d_(T1), T_(P), and (I_(VC)+I_(VB)) using a predetermined calculation formula. As the calculation formula there may be used the following formula (12). d _(T2) =[V _(T) ×d _(T1) +V _(C) ×T _(P) ×D _(C)+(I _(VC) +I _(VB) −V _(C) ×T _(P))×D _(B)]/(V _(T) +I _(VC) +I _(VB))  (12) wherein VT represents the capacity of the developing tank in the automatic developing machine.

Subsequently, at S21, the calculated value d_(T3) of electric conductivity 3 is calculated from d_(T1), (I_(VC)+I_(VB)), and F using a predetermined calculation formula. As the calculation formula there may be used the following formula (13). d _(T3) =[V _(T) ×d _(T1)+(I _(VC) +I _(VB))×F×D _(C)+(I _(VC) +I _(VB))×(1−F)×D _(B)]/(V _(T) +I _(VC) +I _(VB))  (13)

Subsequently, at S22, the integrated value of replenishment rate (I_(VC)+I_(VB)) and the predetermined replenishment amount per each processing (V_(L)) are compared. If the integrated value of replenishment rate (I_(VC)+I_(VB)) is greater than the predetermined replenishment amount per each processing (V_(L)), the processing proceeds to S23. If the integrated value of replenishment rate (I_(VC)+I_(VB)) is not greater than the predetermined replenishment amount per each processing (V_(L)), the processing proceeds to S33.

At S23, if the predetermined value R of replenishment system is a value indicating an electric conductivity-based replenishment system: 1, the processing proceeds to S24. If not, the processing proceeds to S31.

At S24, the electric conductivity of developer d_(M) and the calculated value d_(T2) of electric conductivity 2 are compared. If d_(M) is smaller than d_(T2), the processing proceeds to S25. If not, the processing proceeds to S26.

At S25, a predetermined constant C₁ is added to the predetermined value of time lapse replenishment rate (V_(C)). At S26, C₁ is subtracted from V_(C). On the other hand, at S25, a predetermined constant C₂ is added to the predetermined value of processing replenishment rate (V_(B)). At S26, C₂ is subtracted from V_(B).

Subsequently, at S27, the electric conductivity of developer d_(M) and the calculated value d_(T3) of electric conductivity 3 are compared. If d_(M) is smaller than d_(T2), the processing proceeds to S28. If not, the processing proceeds to S29.

At S28, a predetermined constant C₃ is added to V_(C). At S29, C₃ is subtracted from V_(C). On the other hand, at S28, a predetermined constant C₄ is subtracted from V_(B). At S29, C₄ is added to V_(B).

Subsequently, at S30, the developer is replenished with a replenisher at a rate of (I_(VC)+I_(VB)). The renewal of the values of X and F is preferably carried out as follows. (V _(T) ×X+I _(VC) +I _(VB))/(V _(T) +I _(VC) +I _(VB))→X  (14) (V _(T) ×X+F+I _(VC))/(V _(T) +X+I _(VC) +I _(VB))→F  (15)

Subsequently, at S31, the developer is replenished with a replenisher in an amount of (I_(VC)+I_(VB)). Subsequently, at S32, I_(VC) and I_(VB) are initialized. In some detail, 0 is substituted each in I_(VC) and I_(VB).

At S33, the state of the operation switch of the automatic developing machine is examined. If the operation switch is ON, the processing returns to S12. If the operation switch is OFF, the operation of the automatic developing machine is suspended to finish the processing.

From the above, the controlling of one embodiment of the invention is summarized as follows.

In the controlling of one embodiment of the invention, an electric conductivity of the developer is measured every constant period, a set value of a time lapse replenishment rate is integrated to an integrated value of the time lapse replenishment rate every constant time; a set value of a processing replenishment rate is integrated to an integrated value of the processing replenishment rate every processing of a constant area of a photosensitive lithographic printing plate precursor(s); a percent replenisher replacement which is a ratio of a developer replenishment to a developer in a developing tank is calculated; a percent time lapse replenishment which is a ratio of a time lapse replenisher to a developer in a developing tank is calculated; and thereafter, when a sum of the integrated value of the time lapse replenishment rate and the integrated value of the processing replenishment rate exceeds a value of the lowest replenishment amount, and a set value of a replenishment system indicates an electric conductivity system, steps (A-1), (A-2), (A-3), (A-4), (A-5) and (A-6) are executed, or a set value of a replenishment system does not indicate an electric conductivity system, steps (B-1) and (B-2) are executed: Herein, the execution sequence of the every step may be optionally exchanged.

(A-1) a time elapsed between the last time of replenishment and a present time is measured, and a first calculated value of an electric conductivity is calculated from the elapsed time and the percent replenisher replacement;

(A-2) the set value of the time lapse replenishment rate and the set value of the processing replenishment rate are changed according to a result of a comparison of the first calculated value of the electric conductivity with the measured value of the electric conductivity of the developer;

(A-3) a second calculated value of an electric conductivity is calculated by utilizing the percent replenisher replacement and the percent time replenishment;

(A-4) the set value of the time lapse replenishment rate and the set value of the processing replenishment rate are changed according to a result of a comparison of the second calculated value of the electric conductivity with the measured value of the electric conductivity of the developer;

(A-5) a developer in a developing tank is replenished with a replenisher in an amount corresponding to a sum of the integrated value of the time lapse replenishment rate and the integrated value of the processing replenishment rate; and

(A-6) the integrated value of the time lapse replenishment rate and the integrated value of the processing replenishment rate are initialized,

(B-1) a developer in a developing tank is replenished with a replenisher in an amount corresponding to a sum of the integrated value of the time lapse replenishment rate and the integrated value of the processing replenishment rate; and

(B-2) the integrated value of the time lapse replenishment rate and the integrated value of the processing replenishment rate are initialized.

A third controlling will be described in connection with FIGS. 5, 6 and 7. The third controlling involves controlling dedicated to starting of automatic developing machine in addition to the second controlling shown in FIGS. 3 and 4.

At S41, the integrated value of time lapse replenishment rate (I_(VC)) and the integrated value of processing replenishment rate (I_(VB)), which are each a variable to be used during controlling, are initialized. In some detail, 0 is substituted in these integrated values. Further, it is judged to see if the automatic developing machine has been started for the first time. In the case of first starting, the percent replenisher replacement X and the percent time lapse replenishment F, which are each a variable to be used during controlling, are initialized. In some detail, 0 is substituted in X and C₅ is substituted in F.

At S42, if the predetermined value R of replenishment system is a value indicating an electric conductivity-based replenishment system: 1, the processing proceeds to S43. If not, the processing proceeds to S50.

Subsequently, at S43, it is judged to see if the time which has been elapsed since the starting time or the last time at which the electric conductivity of developer has been measured reaches a predetermined time T_(D). If so, the processing proceeds to S44. If not, the processing proceeds to S49.

At S44, the electric conductivity of the developer is measured. The measured value is then substituted in variable d_(M). Subsequently, at S45, the calculated value d_(T1) of electric conductivity 1 is calculated from the percent replenisher replacement X and the percent time lapse replenishment F using a predetermined calculation formula. As the calculation formula there is preferably used the following formula (14). d _(T1)=(1−X)×D _(M) +X×[(1−F)×D _(B) +F×D _(C)]  (14) wherein D_(M), D_(B) and D_(C) each represents a constant which has been previously determined experimentally.

Subsequently, at S46, d_(M) and d_(T1) are compared. If d_(M) is smaller than d_(T1), the processing proceeds to S47. If not, the processing proceeds to S51.

At S47, the developer is replenished with a replenisher in an amount of V_(L). Subsequently, at S48, the value of X and F are renewed with the value of V_(L). The renewal of the values of X and F is preferably carried out as follows. (V _(T) ×X+V _(L))/(V _(T) +V _(L))→X  (15) (V _(T) ×X×F+V _(L))/(V _(T) ×X+V _(L))→F  (16)

At S49, the state of the operation switch of the automatic developing machine is examined. If the operation switch is ON, the processing returns to S42. If the operation switch is OFF, the operation of the automatic developing machine is suspended to finish the processing.

At S50, the developer in the developing tank is replenished with a replenisher in an amount calculated from the time T_(OFF) during which the automatic developing machine has been suspended. In this case, the calculation of replenishment rate V_(HC) is preferably carried out as follows. V _(HC) =V _(COFF) ×T _(OFF)  (17) wherein V_(COFF) is a constant previously determined experimentally.

The photosensitive material can be subjected to development only when the controlling proceeds to S51. Accordingly, a display may be made at this point that development is made possible.

S51 to S71 are the same as S12 to S32 in the controlling procedure shown in FIGS. 3 and 4 and will not be described hereinafter. The target value of the electric conductivity is renewed with the last replenishment, and the measurement of the electric conductivity and the replenishment of the developer are repeated until the electric conductivity value of the developer exceeds the target value.

At S72, the state of the operation switch of the automatic developing machine is examined. If the operation switch is ON, the processing returns to S51. If the operation switch is OFF, the operation of the automatic developing machine is suspended to finish the processing.

From the above, the controlling of one embodiment of the invention is summarized as follows.

In the controlling of one embodiment of the invention, a value of the electric conductivity at which the developer activity falls within a proper range is calculated as a target value of the electric conductivity; and when a set value of a replenishment system indicates an electric conductivity system shortly after a starting of an operation of the automatic developing machine, steps (C-1), (C-2), (C-3) and (C-4) are executed, or when a set value of a replenishment system does not indicate an electric conductivity system, a developer is replenished with a developer replenisher according to a period of time during which the operation of the automatic developing machine has been suspended. Herein, the execution sequence of the every step may be optionally exchanged.

(C-1) an electric conductivity of the developer is measured every constant period;

(C-2) when the measured value of the electric conductivity of the developer is lower than the target value of the electric conductivity, the developer is replenished with a development replenisher in a predetermined amount;

(C-3) the target value of the electric conductivity is renewed with the replenishment; and

(C-4) the steps (C-1), (C-2) and (C-3) are repeated until the electric conductivity of the developer exceeds the target value of the electric conductivity.

In accordance with the controlling by the aforementioned automatic developing machine, the value of the electric conductivity of the developer can be utilized to make automatic modification of the time lapse replenishment rate/processing replenishment rate. Thus, proper amounts of time lapse replenisher/processing replenisher can be always predetermined against the change of processing conditions, i.e., kind and size of photosensitive material and frequency of processing or atmospheric conditions, i.e., concentration of ambient carbon dioxide gas and wind velocity of atmosphere, making it possible to effect development at a stabilized constant sensitivity. Accordingly, the fluctuation of the developer sensitivity with the change of development conditions can be minimized despite the simple and inexpensive configuration of the development portion of the automatic developing machine. Moreover, even when the electric conductivity sensor is out of order, the replenishment system can be switched to a substitute replenishment system, making it possible to continue the processing of the plate material.

A second embodiment of the present invention is described below. FIG. 8 is a constitutional view of an automatic developing machine according to the second embodiment of the present invention. As shown in FIG. 8, in the automatic developing machine 100 of the embodiment, processing units in the inside thereof are covered with an outer panel 114. Inside the outer panel 114, a developing unit 122 comprising a developing tank 118 for developing a PS plate 112 and an overflow pipe 120 for recovering a developer overflowed from the developing tank 118, a washing unit 124 for water-washing the developer adhered to the PS plate 112, and a finisher unit 126 for desensitizing the washed PS plate 112 by coating a gum solution are disposed. In the washing unit 124, a washing tank 128 is disposed and in the finisher unit 126, a gum solution tank 130 is disposed.

In the outer panel 114, a slit-shaped insert port 202 and a slit-shaped discharge port 204 are provided. In the top surface of the outer panel 114, a reentry insert port (sub-insert port) 250 for insertion of the PS plate 112 between the developing unit 122 and the washing unit 124 is provided. The sub-insert port 250 works as a port for inserting the PS plate 112 in order to perform processing except for the development.

At the sub-insert port 250, a blade 252 is disposed. A leading end of the blade 252 is brought into contact with the outer panel 114 acting as a guiding support surface for the sub-insert port 250, and the base thereof is fixed to the back surface side of the outer panel 114 through a bracket 254. Therefore, the sub-insert port 250 is in the state of being closed by the blade 252.

A drying unit (not shown) dries the PS plate 112 by blowing warm air onto both surfaces thereof as the PS plate 112 delivered from the finisher unit 126 is transported by multiple rollers (not shown).

A pair of transport rollers 132 are disposed on the side of inserting the PS plate 112 into the developing tank 118 of the developing unit 122, and the PS plate 112 is inserted between the pair of transport rollers 132 from the insert port 202.

A rubber-made blade 206 is fixed in the vicinity of the transport roller 132 on the downstream side. A leading end of the blade 206 is brought into contact with the side wall of the developing tank 118 in the developing unit 122, and the base thereof is attached to the outer panel 114 through a bracket 256. The bracket 256 comprises a fixed part 256A and a sliding part 256B attached to the fixed part 256A with a thumbscrew 258, and the blade 206 is fixed to the sliding part 256B. Therefore, in this construction, the leading end of the blade 206 can be separated from the side wall of the developing tank 118 by loosening the thumbscrew 258 and moving the sliding part 256B relative to the fixed part 256A.

Furthermore, in the vicinity of the insert port 202, a plate detection sensor 208 capable of determining the presence or absence of the PS plate 112 and measuring the plate area or the like of the plate transported is attached.

The developing tank 118 has a substantially inverted mountain shape with the top being opened and the bottom center part protruding downward. In the developing tank 118, a pump 260 is provided, and the developer in the developing tank 118 is sucked out by the pump 260 and ejected from spray pipes 144 and 272, which are described later, whereby the developer stored in the developing tank 118 is circulated. During the circulation, the developer passes through an electric conductivity sensor 262 for measuring the electric conductivity of developer. Also, in the developing tank 118, the replenisher stock solution is supplied from a development replenisher stock solution tank 266 through a replenisher stock solution supply pump 264. Furthermore, as described later, diluting water is supplied to the developing tank 118 from the washing tank 128 through a pump 286.

The pumps 264 and 286 are controlled by a controlling device 50 comprising a controlling ROM 51 a or controlling RAM 51 b as a condition memorizing means and a time measuring unit 52, based on signals from the electric conductivity sensor 262 and the time measuring unit 52. The operational effects of the controlling device 50 are same as those described in the first embodiment and they are omitted here.

In the developing tank 118, a guide plate 268 is disposed on the upstream side, and many guide rollers 134 and a rotary brush roller 270 are disposed on the downstream side. The guide rollers 134 and rotary brush roller 270 are rotatably bridged over a pair of side boards of the developing tank 118.

A guide roller 136 having a relatively large diameter is disposed above the guide plate 268, and rotary brush rollers 138 and 270 and a guide roller 140 are disposed above the guide roller 134. Also, in the center part of the developing tank 118, a pair of squeeze rollers 142 having a function of squeezing the surface of the PS plate 112 are disposed.

The overflow pipe 120 is disposed on the most downstream side of the developing tank 118 and when the liquid surface of the developer exceeds a predetermined level, the developer is guided by the pipe to a waste solution tank 284.

A liquid surface cover 150 is disposed on the surface of developer in the developing tank 118. The liquid surface cover 150 is protruding nearly like an arc at the portion corresponding to the rotary brush roller 138 and guide roller 140 adjacent thereto, and contacting with the liquid surface of developer so as to maximally prevent the developer from contacting with air. Also, the liquid surface cover 150 is slidably held at its both edges in the transport direction of the PS plate 112 by the side boards (not shown) in such a manner as to permit a vertical motion of the cover in accordance with increase or decrease of the developer.

The end of the liquid surface cover 150 on the downstream side in the transport direction is brought into contact with a leading end of a blade 274. The blade 274 is fixed to the outer panel 114 via a bracket 276. The liquid surface of the developer exposed at the downstream end of the liquid cover 150 in the transport direction is separated by the blade 274 from the space above the liquid surface cover 150, and thus the space above the liquid surface cover 150 is perfectly isolated from external air by the blade 206 (in the state of contacting with the side wall of the developing tank 118) in the vicinity of the insert port 202, whereby the developer can be prevented from evaporation.

On the most downstream side of the developing tank 118 in the transport direction, a pair of rollers 154 for holding and transporting the PS plate 112 and at the same time, squeezing the developer from the surface of the PS plate 112 are disposed.

On the other hand, in the automatic developing machine 100, the washing tank 128 of the washing unit 124 is disposed on the downstream side of the developing unit 122, and two pairs of transport rollers 152 and 153 are disposed above the washing tank 128.

The washing tank 128 stores washing water used for washing out the developer on the PS plate 112 delivered from the developing tank 118. A spray pipe 156 is disposed on the upstream side of the transport roller 153 and above the transport passage. In the outer circumference of the spray pipe 156, a plurality of ejection ports communicating with the inside are provided. The washing water pumped up by the pump 280 from the washing water tank 278 is dropped from the spray pipe 156 on the upper roller of the transport rollers 153 and with the rotation of the transport roller 153, the washing water rapidly spreads on the surface of the PS plate 112, whereby the surface of the PS plate 112 is cleaned with the washing water.

The lower roller of the transport roller 152 or 153 is housed at its bottom in a pan 162. The pan 162 stores washing water, and the washing water is scooped up by the lower roller and used to clean the back surface of the PS plate 112 and also prevent the drying of the upper transport roller 152 or 153.

The washing water spread laterally on the front surface of the PS plate 112 falls into the pan 162 from both ends in the crosswise direction of the PS plate 112, and the washing water scooped up from the pan 162 is used to treat the back surface of the PS plate 112. The washing water overflowed from the pan 162 is guided into the washing tank 128. In the washing tank 128, an overflow pipe 282 is disposed and when the waste water exceeds a predetermined liquid surface, the washing water is discarded into the waste solution tank 284.

The washing tank 128 and the developing tank 118 are communicating with each other via a pump 286 and when the pump 286 is driven, the washing water in the washing tank 128 is guided into the developing tank 118 and can be used as a diluent at the time of supplying the replenisher stock solution to the developing tank 118.

A pair of transport rollers 178 are provided above the gum solution tank 130 of the finisher unit 126. The PS plate 112 delivered by the transport rollers 153 is guided to the transport rollers 178.

On the upstream side of the transport rollers 178, spray pipes 182 and 288 are disposed above the transport passage and below the transport passage, respectively. The gum solution pumped up by a pump 292 from the gum solution tank 290 is ejected from the spray pipe 182 or 288 and supplied to the front or back surface of the PS plate 112.

The transport rollers 178 hold and transport the PS plate 112 and at the same time, squeeze the gum solution supplied by the spray pipe 182 for desensitizing the surface of the PS plate 112. The gum solution squeezed off from the surface of the PS plate 112 is recovered in the gum solution tank 130. The gum solution in the gum solution tank 130 is circulated by the pump 294. In the gum solution tank 130, an overflow pipe 296 is provided and when the gum solution exceeds a predetermined liquid surface, the gum solution is guided to and discarded in the waste solution tank 284.

The bottom of the lower transport roller 178 is immersed in the gum solution stored in the gum solution tank 130, and the gum solution is scooped up by the lower transport roller 178 from the gum solution tank 130 and coated on the back surface of the PS plate 112, whereby the back surface of the PS plate 112 is desensitized with the gum solution scooped up by the transport roller 178 and at the same time, the upper transport roller 178 is prevented from drying so as not to deposit components of the processing solution on the surface of the transport roller 178.

The PS plate 112 after the completion of treatments in the finisher unit 126 is delivered to the drying unit (not shown) through the discharge port 204 of a casing 200.

A lid body 210 serving as a shutter is provided at the discharge port 204. The lid body 210 is fixed to a shaft 212. The shaft 212 is made rotatable by a driving device (for example, a solenoid) (not shown). The shaft 212 rotates based on the detection of PS plate 112 by the plate detection sensor 208 provided in the vicinity of the insert port 202. More specifically, the lid body 210 is kept at a substantially horizontal position (opened state of discharge port 204) during the time of detecting the PS plate 112 by the plate detection sensor 208 and during the passage of a predetermined time after the plate is not detected (after the rear end is detected), or otherwise kept at a vertical position (closed state of discharge port 204).

The operation of the embodiment is described below. The processing tanks, for example, developing tank 118, washing tank 128 and gum solution tank 130 are covered with a casing 200, for example, top cover 114 and main body 108. In the case where the development of PS plate 112 is not being processed in the automatic developing machine 100, the blade 206 is brought into contact with the side wall of the developing tank 118 and therefore, the insert port 202 is closed. Also, the plate detection sensor 208 does not detect the PS plate 112 and therefore, the lid body 210 is in the vertical position to close the discharge port 204. Furthermore, the sub-insert port 250 is also closed by the blade 252, and the space above the liquid surface cover 150 of the developing unit 122 is also closed by the blades 206 and 122. Accordingly, the developer in the developing tank 118, the washing water in the washing unit 124 and the gum solution in the finisher unit 126 are protected from exposure to external air and substantially free of carbon dioxide fatigue. As a result, the developing capability can be prevented from reduction due to time lapse deterioration and therefore, the replenishment amount, for example, of the replenisher stock solution in the developing unit 122 can be drastically reduced. In particular, the developer surface of the developing tank 118 is covered with the liquid surface cover 150 and therefore, the effect of preventing the developer from contact with external air is large.

Further, the lid body 210 is preferably made open as short as possible so as to minimize the contact of developer with external air. Accordingly, in a preferred constitution, the lid body is opened only when the PS plate 112 is passing, and closed at other times.

The contents of control by the controlling device 50 is same as the contents in the flow chart showing the replenishment method of the development replenisher in FIGS. 2 to 7 described above for the first embodiment and therefore, the description thereof is omitted here.

EXAMPLE

A fluctuation range of developer sensitivity was experimentally determined in the case where the replenishment method for development replenisher according to the embodiment described above or a conventional replenishment method for development replenisher was performed. Methods for production of Developers A, B, C and D, Replenishers A, B, C and D, and Photosensitive Materials A, B, C, D and E used in Examples 1 to 10 and Comparative Examples 1 to 20 are described below.

[Developer A]

Developer A was prepared by diluting Developer DP-7 (produced by Fuji Photo Film Co., Ltd.) with water to be 1/9.

[Developer B]

Developer B was prepared by diluting Developer DT-2 (produced by Fuji Photo Film Co., Ltd.) with water to be 1/9.

[Developer C]

Developer C was prepared by dissolving the components shown below in water and adjusting pH to the value shown below with KOH.

Surfactant shown below   5% by mass 2,4,7,9-Tetramethyl-5-decyn-4,7-diol  0.1% by mass Tetrasodium ethylenediaminetetraacetate  0.2% by mass Potassium carbonate  0.2% by mass pH (25° C.) 12.0

[Developer D]

Developer D was prepared by dissolving the components shown below in water and adjusting pH to the value shown below with KOH.

Compound of formula (I): (Y) shown below   50 g Tetrasodium ethylenediaminetetraacetate  0.1 g Additive 1: (P) shown below  1.0 g Additive 2: (Q) shown below  1.0 g pH (25° C.) 12.0 (Y)

(P)

(Q)

[Replenisher A]

Development Replenisher DP-7RW (produced by Fuji Photo Film Co., Ltd.) was used.

[Replenisher B]

Development Replenisher DT-2R (produced by Fuji Photo Film Co., Ltd.) was used.

[Replenisher C]

Replenisher C was prepared by dissolving the components shown below in water and adjusting pH to the value shown below with KOH.

Surfactant shown below   5% by mass 2,4,7,9-Tetramethyl-5-decyn-4,7-diol  0.1% by mass Tetrasodium ethylenediaminetetraacetate  0.2% by mass Potassium carbonate  0.2% by mass pH (25° C.) 13.0

[Replenisher D]

Replenisher D was prepared by dissolving the components shown below in water and adjusting pH to the value shown below with KOH.

Compound of formula (I): (Y) shown below   50 g Tetrasodium ethylenediaminetetraacetate  0.1 g Additive 1: (P) shown below  1.0 g Additive 2: (Q) shown below  1.0 g pH (25° C.) 13.0 (Y)

(P)

(Q)

[Photosensitive Material A]

Photosensitive Material A was prepared based on Example 1 of JP-A-2000-231188. The photosensitive plate precursor thus-obtained was imagewise exposed by Printer FT26V2UPNS (light source: 2 kW metal halide lamp, produced by Nuark in USA) for one minute.

[Photosensitive Material B]

Photosensitive Material B was prepared based on Example 1 of JP-A-7-295212. The photosensitive plate precursor thus-obtained was imagewise exposed by Printer FT26V2UPNS (light source: 2 kW metal halide lamp, produced by Nuark in USA) in 50 counts.

[Photosensitive Material C]

A 0.3 mm-thick aluminum plate (material: 1050) was cleansed with trichloroethylene to degrease. Then, the surface of aluminum plate was grained using a nylon brush and a 400-mesh pumice-water suspension, followed by thoroughly washing with water. After the washing, the aluminum plate was dipped in a 25% aqueous sodium hydroxide solution at 45° C. for 9 seconds to conduct etching, washed with water, further dipped in a 20% aqueous nitric acid solution for 20 seconds, and again washed with water. At this time, an etching amount of the grained surface was about 3 g/m². Subsequently, the aluminum plate was treated using 7% sulfuric acid as an electrolytic solution and passing direct current of a current density of 15 A/dm² to provide an anodic oxide film of 3 g/m², then washed with water and dried. The aluminum plate was treated with a 2.5% aqueous sodium silicate solution at 30° C. for 10 seconds and then, a coating solution for undercoat layer shown below was coated and dried at 80° C. for 15 seconds, thereby preparing a support. A coating amount of the undercoat layer after drying was 15 mg/m².

<Coating Solution for Undercoat Layer>

Copolymer P shown below (molecular weight: 28,000)  0.3 g Methanol 100 g Water  1 g Copolymer P

<Synthesis of Specific Copolymer> Synthesis Example (Synthesis of Specific Copolymer 1)

Into a 500 ml-volume three-necked flask equipped with a stirrer, a condenser tube and a dropping funnel were charged 31.0 g (0.36 mol) of methacrylic acid, 39.1 g (0.36 mol) of ethyl chloroformate and 200 ml of acetonitrile, and the resulting mixture was stirred under cooling in an ice water bath. To the mixture, 36.4 g (0.36 mol) of triethylamine was added dropwise through the dropping funnel over a period of about one hour. After the completion of the dropwise addition, the ice water bath was removed, and the mixture was stirred at room temperature for 30 minutes. To the reaction mixture was added 51.7 g (0.30 mol) of p-aminobenzenesulfonamide, and the resulting mixture was stirred for one hour while heating to 70° C. on an oil bath. After the completion of the reaction, the reaction mixture was poured into one liter of water while stirring the water, and the resulting mixture was stirred for 30 minutes. The mixture was filtered to collect deposit and the deposit was made into a slurry with 500 ml of water. The slurry was filtered and the resulting solid was dried to obtain a white solid of N-(p-aminosulfonylphenyl)methacrylamide (yield: 46.9 g).

Subsequently, 4.61 g (0.0192 mol) of N-(p-aminosulfonylphenyl)methacrylamide, 2.94 g (0.0258 mol) of ethyl methacrylate, 0.80 g (0.015 mol) of acrylonitrile and 20 g of N,N-dimethylacetamide were charged into a 20 ml-volume three-necked flask equipped with a stirrer, a condenser tube and a dropping funnel, and the resulting mixture was stirred under heating to 65° C. on a hot water bath. To the mixture was added 0.15 g of V-65 (produced by Wako Pure Chemical Industries, Ltd.), and the resulting mixture was stirred under a nitrogen stream while keeping the temperature at 65° C. for 2 hours. To the reaction mixture was further added dropwise a mixture containing 4.61 g of N-(p-aminosulfonylphenyl)methacrylamide, 2.94 g of ethyl methacrylate, 0.80 g of acrylonitrile, N,N-dimethylacetamide and 0.15 g of V-65 through the dropping funnel over a period of 2 hours. After the completion of the dropwise addition, the resulting mixture was further stirred at 65° C. for 2 hours. After the completion of the reaction, 40 g of methanol was added to the mixture, and the resulting mixture was cooled and poured into 2 liters of water while stirring the water, followed by stirring for 30 minutes. Then, the deposit was collected by filtration and dried to obtain 15 g of a white solid. A weight average molecular weight of the resulting specific copolymer measured by gel permeation chromatography and calculated in terms of standard polystyrene was 53,000.

On the support described above, a coating solution for image recording layer shown below was coated to have a dry coating amount of 1.8 g/m² to prepare a positive infrared-sensitive lithographic printing plate precursor.

<Coating Solution for Image Recording Layer>

Copolymer 1 shown above  0.4 g m, p-Cresol novolak (m/p ratio = 6/4, weight average  0.6 g molecular weight: 8,000, containing 0.5% of unreacted cresol) Cyanine Dye A shown hereinbefore  0.1 g Phthalic anhydride 0.05 g p-Toluenesulfonic acid 0.002 g  Ethyl Violet (counter ion: 6-hydroxy-β-naphthalenesulfonic 0.02 g acid) Esterified product of naphthoquinone-1,2-diazido-5-sulfonyl 0.01 g chloride and pyrogallol-acetone resin Fluorine-containing surfactant (Megafac F-177, produced 0.05 g Dai-Nippon Ink & Chemicals, Inc.) Methyl ethyl ketone   8 g 1-Methoxy-2-propanol   4 g [Photosensitive Material D] [Preparation of Support] <Aluminum Plate>

Molten metal was prepared using an aluminum alloy containing 0.06% by mass of Si, 0.30% by mass of Fe, 0.001% by mass of Cu, 0.001% by mass of Mn, 0.001% by mass of Mg, 0.001% by mass of Zn and 0.03% by mass of Ti and balance of Al and unavoidable impurities, subjected to molten metal treatment and filtration, and made into an ingot of 500 mm in thickness and 1200 mm in width according to a DC casting method. After cutting the surface to a depth of 10 mm on the average using a planer, the ingot was uniformly kept at 550° C. for about 5 hours, and when the temperature of the ingot decreased to 400° C., it was rolled into a 2.7-mm thick rolled plate using a hot rolling machine. Further, it was subjected to thermal treatment at 500° C. using a continuous annealing machine, and then finished into a 0.24-mm thick plate by cold rolling to obtain an aluminum plate of JIS 1050 material. The aluminum plate was cut into pieces of 1030 mm in width, and then subjected to the surface treatment shown below.

<Surface Treatment>

The surface treatment is carried out by continuously subjecting the aluminum plate to the various treatments (a) to (j) shown below in order. Each of the treatments and washings was followed by removing the remaining liquid by means of nip rollers.

(a) Mechanical Surface-Roughening Treatment

Mechanical surface-roughening treatment of the aluminum plate was conducted by means of rotating roller-form nylon brushes while supplying a suspension of an abrasive (pumice) in water having specific gravity of 1.12 as an abrasion slurry solution to the surface of the aluminum plate. An average particle size of the abrasive was 30 μm, with the maximum particle size being 100 μm. A material of the nylon brush was 6-10 nylon, and the brush has a bristle length of 45 mm and a bristle diameter of 0.3 mm. The nylon brush was made by making holes in a stainless steel cylinder having a diameter of 300 mm and densely filling the brush bristles. Three of the rotating nylon brushes were used. Two supporting rollers (having a diameter of 200 mm) provided under the brush rollers were spaced 300 mm. The brush rollers were pressed against the aluminum plate till the load applied to a driving motor for rotating the brush became 7 kW greater than the load before pressing the brush rollers against the aluminum plate. The rotating direction of the brushes was the same as the moving direction of the aluminum plate. The rotation number of the brushes was 200 rpm.

(b) Alkali-Etching Treatment

Etching treatment of the aluminum plate was conducted by spraying an aqueous solution having a sodium hydroxide concentration of 2.6% by mass, an aluminum ion concentration of 6.5% by mass and temperature of 70° C. to dissolve the aluminum plate in an amount of 10 g/m², followed by washing with water by spraying.

(c) Desmut Treatment

Desmut treatment of the aluminum plate was conducted by spraying an aqueous solution having temperature of 30° C. and a nitric acid concentration of 1% by mass (containing 0.5% by mass of aluminum ion), followed by washing with water by spraying. The aqueous nitric acid solution used for the desmut treatment was a waste solution from the step of conducting electrochemical surface-roughening treatment in an aqueous nitric acid solution using alternating current described below.

(d) Electrochemical Surface-Roughening Treatment

Electrochemical surface-roughening treatment of the aluminum plate was continuously conducted by applying a 60 Hz alternating current voltage. The electrolytic solution used was an aqueous solution containing 10.5 g/liter of nitric acid (containing 5 g/liter of aluminum ion and 0.007% by mass of ammonium ion) and having solution temperature of 50° C. The electrochemical surface-roughening treatment was conducted using an alternating current source, which provides a trapezoidal rectangular wave alternating current where time (TP) for reaching the current to its peak from zero was 0.8 msec and duty ratio was 1:1, and using a carbon electrode as a counter electrode. A ferrite was used as an auxiliary anode.

The current density was 30 A/dm² at the peak current, and the electric amount was 220 C/dm² in terms of the total electric amount during the aluminum plate functioning as an anode. To the auxiliary anode, 5% of the current from the electric source was provided. Subsequently, the plate was washed with water by spraying.

(e) Alkali-Etching Treatment

Etching treatment of the aluminum plate was conducted at 32° C. by spraying an aqueous solution having a sodium hydroxide concentration of 26% by mass and an aluminum ion concentration of 6.5% by mass to dissolve the aluminum plate in an amount of 0.50 g/m². Thus, the smut component mainly comprising aluminum hydroxide formed in the precedent electrochemical surface-roughening treatment using alternating current was removed and an edge portion of the pit was dissolved away to smoothen the edge portion. Subsequently, the plate was washed with water by spraying.

(f) Desmut Treatment

Desmut treatment of the aluminum plate was conducted by spraying an aqueous solution having temperature of 30° C. and nitric acid concentration of 15% by mass (containing 4.5% by mass of aluminum ion), followed by washing with water by spraying. The aqueous nitric acid solution used for the desmut treatment was a waste solution from the step of conducting electrochemical surface-roughening treatment in an aqueous nitric acid solution using alternating current described above.

(g) Electrochemical Surface-Roughening Treatment

Electrochemical surface-roughening treatment of the aluminum plate was continuously conducted by applying a 60 Hz alternating current voltage. The electrolytic solution used was an aqueous solution containing 50 g/liter of hydrochloric acid (containing 5 g/liter of aluminum ion) and having temperature of 35° C. The electrochemical surface-roughening treatment was conducted using an alternating current source, which provides a trapezoidal rectangular wave alternating current where time (TP) for reaching the current to its peak from zero was 0.8 msec and duty ratio was 1:1, and using a carbon electrode as a counter electrode. A ferrite was used as an auxiliary anode.

The current density was 25 A/dm² at the peak current, and the electric amount was 50 C/dm² in terms of the total electric amount during the aluminum plate functioning as an anode. Subsequently, the plate was washed with water by spraying.

(h) Alkali-Etching Treatment

Etching treatment of the aluminum plate was conducted at 32° C. by spraying an aqueous solution having a sodium hydroxide concentration of 26% by mass and an aluminum ion concentration of 6.5% by mass to dissolve the aluminum plate in an amount of 0.10 g/m². Thus, the smut component mainly comprising aluminum hydroxide formed in the precedent electrochemical surface-roughening treatment using alternating current was removed and an edge portion of the pit was dissolved away to smoothen the edge portion. Subsequently, the plate was washed with water by spraying.

(i) Desmut Treatment

Desmut treatment of the aluminum plate was conducted by spraying an aqueous solution having temperature of 60° C. and sulfuric acid concentration of 25% by mass (containing 0.5% by mass of aluminum ion), followed by washing with water by spraying.

(j) Anodizing Treatment

Anodizing treatment of the aluminum plate was conducted using an anodizing treatment apparatus. A sulfuric acid solution was used as an electrolytic solution supplied to a first and second electrolytic units. The electrolytic solution had sulfuric acid concentration of 170 g/liter (containing 0.5% by mass of aluminum ion) and temperature of 38° C. Subsequently, the plate was washed with water by spraying. The final oxide film amount was 2.7 g/m².

The surface roughness (Ra) of the resulting aluminum support was 0.45.

[Undercoat]

An undercoat solution shown below was coated on the aluminum support by a wire bar and dried at 90° C. for 30 seconds using a hot air drying apparatus. A coating amount of the undercoat after drying was 10 mg/m².

<Undercoat Solution>

Copolymer of ethyl acrylate and sodium salt of 0.1 g 2-acrylamido-2-methyl-1-propanesulfonate (75:15 in molar ratio) 2-Aminoethylphosphonic acid 0.1 g Methanol  50 g Ion-exchanged water  50 g [Photosensitive Layer]

A coating solution for photosensitive layer [P-1] shown below was prepared and coated on the aluminum support having the undercoat described above by a wire bar, followed by drying at 122° C. for 43.5 seconds using a hot air drying apparatus to form a photosensitive layer. A coverage of the photosensitive layer after drying was 1.4 g/m².

<Coating Solution for Photosensitive Layer [P-1]>

Infrared absorber (IR-1) shown below 0.08 g Polymerization Initiator (OS-1) shown below 0.25 g Dipentaerythritol hexaacrylate 1.00 g Binder Polymer (BT-1) shown below 1.00 g Chloride salt of Ethyl Violet 0.04 g Fluorine-containing surfactant (Megafac F-780-F, produced 0.03 g Dai-Nippon Ink & Chemicals, Inc.) Methyl ethyl ketone 10.4 g Methanol 4.83 g 1-Methoxy-2-propanol 10.4 g

The structures of Infrared absorber (IR-1), Polymerization Initiator (OS-1) and Binder Polymer (BT-1) are shown below.

[Protective Layer (Overcoat Layer)]

An aqueous solution of a mixture of polyvinyl alcohol (saponification degree: 98% by mole; polymerization degree: 500) and polyvinyl pyrrolidone (Luviskol K-30, produced by BASF) was coated on the surface of the photosensitive layer by a wire bar and dried at 125° C. for 75 seconds using a hot air drying apparatus. The content of polyvinyl alcohol was 85% by mass. A coating amount (coverage after drying) of the protective layer was 2.45 g/m². A dynamic friction coefficient of the surface was 0.45. Thus, Photosensitive Material D was prepared.

[Photosensitive Material E]

A 0.3 mm-thick aluminum plate of IS material was thoroughly washed with water, dipped in a 10% aqueous sodium hydroxide solution at 70° C. for 60 seconds to conduct etching, washed with running water, and treated with 20% nitric acid to neutralize and cleanse, followed by washing with water. The aluminum plate was then subjected to electrolytic surface-roughening treatment in a 1.5% aqueous nitric acid solution using an alternating waveform current of a sign wave under the condition of V_(A) of 12.7 V in an amount of electricity of 270 coulomb/dm² at anode. The surface roughness of the plate measured was 0.30 μm (in Ra). Subsequently, the plate was dipped in a 30% aqueous sulfuric acid solution at 40° C. for 2 minutes to conduct desmutting and then subjected to anodic oxidation in a 20% aqueous sulfuric acid solution at 33° C. in a current density of 5 A/dm² for 50 seconds while arranging an cathode on the side of the grained surface of the plate to form an anodic oxide film having a thickness of 2.7 g/m².

A coating solution for intermediate layer having the composition shown below was coated on the aluminum plate thus-treated and dried so as to have a dry coating amount of 2 mg/m² and dried at 100° C. for 3 minutes.

<Coating Solution for Intermediate Layer>

The composition shown below was mixed and stirred, and after about 5 minutes, generation of heat was observed. After the reaction for 60 minutes, 20,000 g of methanol was added to the reaction mixture.

Methanol 100 g  DDP-8 (phosphoric acid compound, produced by Nikko 15 g Chemical Co., Ltd.) Water 10 g Phosphoric acid  5 g Tetraethoxysilane 50 g 3-Methacryloxypropyltriethoxysilane 50 g

A high-sensitive photopolymerizable composition 1 having the composition shown below was coated on the intermediate layer so as to have a dry coating amount of 1.5 g/m² and dried at 100° C. for 90 seconds to prepare a photosensitive layer.

<Photopolymerizable Composition 1>

Ethylenically Unsaturated Bond-Containing Compound (A1)  1.8 g shown below Linear Organic Polymer Binder (B1)  1.5 g Sensitizer (C1) 0.15 g Photo-Initiator (D1)  0.2 g Dispersion of β-phthalocyanine (F1)  0.2 g Fluorine-containing nonionic surfactant (Megafac F177, 0.03 g produced Dai-Nippon Ink & Chemicals, Inc.) Methyl ethyl ketone   10 g Propylene glycol monomethyl ether acetate   10 g A1

B1

C1

D1

F1

A 3% by mass aqueous solution of polyvinyl alcohol (saponification degree: 98% by mole; polymerization degree: 500) was coated on the photopolymerizable photosensitive layer thus-prepared so as to have a dry coating amount of 2.5 g/m² and dried at 100° C. for 90 seconds to prepare Photosensitive Material E.

PROCESSING IN EXAMPLES 1 TO 10

As set forth in Tables 1 to 5, continuous processing was effected using the replenishment method of the invention to evaluate the sensitivity stability of the developer. For the evaluation of stability of developer sensitivity, how much the density of the image having a gradation of 50% obtained by halftone-exposing a photosensitive material changes after development was examined. The results are set forth in Table 8.

PROCESSING IN COMPARATIVE EXAMPLES 1 TO 20

As set forth in Tables 1 to 5, the photosensitive lithographic printing plate precursors were continuously processed using an area and time lapse-based replenishment system and an electric conductivity-based replenishment system to evaluate the stability of developer sensitivity. For the evaluation of stability of developer sensitivity, how much the density of the image having a gradation of 50% obtained by halftone-exposing a photosensitive material changes after development was examined. The results are set forth in Table 8.

TABLE 1 Halftone Processing Forming Replenishment system Photosensitive Material Developer Replenisher Condition Method Example 1 System of Present Invention Photosensitive Material A Photosensitive Developer A Replenisher A Processing Screening E (control system shown in Material B Condition 1 FIGS. 3, 4) Example 2 System of Present Invention Photosensitive Material A Photosensitive Developer B Replenisher B Processing Screening E (control system shown in Material B Condition 2 FIGS. 3, 4) Photosensitive Material C Example 3 System of Present Invention Photosensitive Material D Developer C Replenisher C Processing Screening E (control system shown in Condition 3 FIGS. 3, 4) Example 4 System of Present Invention Photosensitive Material E Developer D Replenisher D Processing Screening E (control system shown in Condition 4 FIGS. 3, 4) Example 5 System of Present Invention Photosensitive Material E Developer D Replenisher D Processing Screening E (control system shown in Condition 4 FIGS. 3, 4) Example 6 System of Present Invention Photosensitive Material A Photosensitive Developer A Replenisher A Processing Screening A (control system shown in Material B Condition 1 FIGS. 3, 4) Example 7 System of Present Invention Photosensitive Material A Photosensitive Developer B Replenisher B Processing Screening B (control system shown in Material B Condition 2 FIGS. 3, 4) Photosensitive Material C Example 8 System of Present Invention Photosensitive Material D Developer C Replenisher C Processing Screening B (control system shown in Condition 3 FIGS. 3, 4) Example 9 System of Present Invention Photosensitive Material E Developer D Replenisher D Processing Screening C (control system shown in Condition 4 FIGS. 3, 4) Example 10 System of Present Invention Photosensitive Material E Developer D Replenisher D Processing Screening D (control system shown in Condition 4 FIGS. 3, 4) Comparative Area and Time Lapse-Based Photosensitive Material A Photosensitive Developer A Replenisher A Processing Screening E Example 1 Replenishment System Material B Condition 5 (no conductivity detection) Comparative Area and Time Lapse-Based Photosensitive Material A Photosensitive Developer B Replenisher B Processing Screening E Example 2 Replenishment System Material B Condition 6 (no conductivity detection) Photosensitive Material C Comparative Area and Time Lapse-Based Photosensitive Material D Developer C Replenisher C Processing Screening E Example 3 Replenishment System Condition 7 (no conductivity detection) Comparative Area and Time Lapse-Based Photosensitive Material E Developer D Replenisher D Processing Screening E Example 4 Replenishment System Condition 8 (no conductivity detection) Comparative Area and Time Lapse-Based Photosensitive Material E Developer D Replenisher D Processing Screening E Example 5 Replenishment System Condition 8 (no conductivity detection) Comparative Area and Time Lapse-Based Photosensitive Material A Photosensitive Developer A Replenisher A Processing Screening A Example 6 Replenishment System Material B Condition 5 (no conductivity detection) Comparative Area and Time Lapse-Based Photosensitive Material A Photosensitive Developer B Replenisher B Processing Screening B Example 7 Replenishment System Material B Condition 6 (no conductivity detection) Photosensitive Material C Comparative Area and Time Lapse-Based Photosensitive Material D Developer C Replenisher C Processing Screening B Example 8 Replenishment System Condition 7 (no conductivity detection) Comparative Area and Time Lapse-Based Photosensitive Material E Developer D Replenisher D Processing Screening C Example 9 Replenishment System Condition 8 (no conductivity detection) Comparative Area and Time Lapse-Based Photosensitive Material E Developer D Replenisher D Processing Screening D Example 10 Replenishment System Condition 8 (no conductivity detection) Comparative Electric Conductivity-Based Photosensitive Material A Photosensitive Developer A Replenisher A Processing Screening E Example 11 Replenishment System Material B Condition 9 Comparative Electric Conductivity-Based Photosensitive Material A Photosensitive Developer B Replenisher B Processing Screening E Example 12 Replenishment System Material B Condition 10 Photosensitive Material C Comparative Electric Conductivity-Based Photosensitive Material D Developer C Replenisher C Processing Screening E Example 13 Replenishment System Condition 11 Comparative Electric Conductivity-Based Photosensitive Material E Developer D Replenisher D Processing Screening E Example 14 Replenishment System Condition 12 Comparative Electric Conductivity-Based Photosensitive Material E Developer D Replenisher D Processing Screening E Example 15 Replenishment System Condition 12 Comparative Electric Conductivity-Based Photosensitive Material A Photosensitive Developer A Replenisher A Processing Screening A Example 16 Replenishment System Material B Condition 19 Comparative Electric Conductivity-Based Photosensitive Material A Photosensitive Developer B Replenisher B Processing Screening B Example 17 Replenishment System Material B Condition 10 Photosensitive Material C Comparative Electric Conductivity-Based Photosensitive Material D Developer C Replenisher C Processing Screening B Example 18 Replenishment System Condition 11 Comparative Electric Conductivity-Based Photosensitive Material E Developer D Replenisher D Processing Screening C Example 19 Replenishment System Condition 12 Comparative Electric Conductivity-Based Photosensitive Material E Developer D Replenisher D Processing Screening D Example 20 Replenishment System Condition 12

TABLE 2 Time Lapse Replenishment Time Lapse Change of Automatic Volume of Amount in Replenishment Processing ambient carbon Developing Developing Development Development Operating Amount in Replenishment Processing dioxide gas Machine Tank Temperature Time Time Stopped time amount Pattern concentration Processing FIG. 8 20,000 cc 30° C. 12 sec. — — — Table 3 Table 6 Condition 1 Processing FIG. 1 20,000 cc 30° C. 12 sec. — — — Table 4 Table 6 Condition 2 Processing FIG. 1 20,000 cc 30° C. 12 sec. — — — Table 5 Table 6 Condition 3 Processing FIG. 1 20,000 cc 28° C. 18 sec. — — — Table 5 Table 6 Condition 4 Processing FIG. 8 20,000 cc 30° C. 12 sec. 220 cc/h 100 cc/h 40 cc/m² Table 3 Table 6 Condition 5 Processing FIG. 1 20,000 cc 30° C. 12 sec.  50 cc/h  15 cc/h 20 cc/m² Table 4 Table 6 Condition 6 Processing FIG. 1 20,000 cc 30° C. 12 sec. ² Table 5 Table 6 Condition 7 Processing FIG. 1 20,000 cc 28° C. 18 sec. ² Table 5 Table 6 Condition 8 Processing FIG. 8 20,000 cc 30° C. 12 sec. — — — Table 3 Table 6 Condition 9 Processing FIG. 1 20,000 cc 30° C. 12 sec. — — — Table 4 Table 6 Condition 10 Processing FIG. 1 20,000 cc 30° C. 12 sec. — — — Table 5 Table 6 Condition 11 Processing FIG. 1 20,000 cc 28° C. 18 sec. — — — Table 5 Table 6 Condition 12

TABLE 3 Processing Amount per Day (area of plate × number of sheets of plate) Day 1st 2nd 3rd 4th 5th 8th 9th 10th 11th 12th Day of Week Mon Tue Wed Thu Fri Mon Tue Wed Thu Fri PHOTOSENSITIVE AM 0.8 × 13 0.8 × 13 0.8 × 13 0.8 × 42 0.8 × 7 0 0.8 × 7 0 0.8 × 7 0.8 × 4 MATERIAL A PM 0.8 × 13 0.8 × 13 0.8 × 13 0.8 × 42 0.8 × 7 0 0.8 × 7 0 0.8 × 7 0.8 × 4 (m² × plate) PHOTOSENSITIVE AM 0 0 0 0 0 0.8 × 7 0 0.8 × 7 0 0 MATERIAL B PM 0 0 0 0 0 0.8 × 7 0 0.8 × 7 0 0 (m² × plate) Total (m²) 21  21  21  67  11  11  11  11  11  6

TABLE 4 Processing Amount per Day (area of plate × number of sheets of plate) Day 1st 2nd 3rd 4th 5th 8th 9th 10th 11th 12th Day of Week Mon Tue Wed Thu Fri Mon Tue Wed Thu Fri PHOTOSENSITIVE AM 0 0 0 0 0 0.8 × 3 0 0.8 × 3 0 0 MATERIAL A PM 0 0 0 0 0 0.8 × 4 0 0.8 × 4 0 0 (m² × plate) PHOTOSENSITIVE AM 0.8 × 6 0.8 × 6 0.8 × 6 0.8 × 20 0.8 × 3 0 0.8 × 3 0 0.8 × 3 0 MATERIAL B PM 0.8 × 7 0.8 × 7 0.8 × 7 0.8 × 20 0.8 × 4 0 0.8 × 4 0 0.8 × 4 0 (m² × plate) PHOTOSENSITIVE AM 0.8 × 6 0.8 × 6 0.8 × 6 0.8 × 22 0.8 × 3 0.5 × 3 0.8 × 3 0.5 × 3 0.8 × 3 0.8 × 2 MATERIAL C PM 0.8 × 7 0.8 × 7 0.8 × 7 0.8 × 22 0.8 × 4 0.5 × 4 0.8 × 4 0.5 × 4 0.8 × 4 0.8 × 2 (m² × plate) Total (m²) 21  21  21 67  11  9 11  9 11  3

TABLE 5 Processing Amount per Day (area of plate × number of sheets of plate) Day 1st 2nd 3rd 4th 5th 8th 9th 10th 11th 12th Day of Week Mon Tue Wed Thu Fri Mon Tue Wed Thu Fri PHOTO- AM 0.8 × 13 0.8 × 13 0.8 × 13 0.8 × 42 0.8 × 7 0.4 × 14 0.4 × 14 0.4 × 14 0.4 × 14 0.4 × 8 SENSITIVE PM 0.8 × 13 0.8 × 13 0.8 × 13 0.8 × 42 0.8 × 7 0.4 × 14 0.4 × 14 0.4 × 14 0.4 × 14 0.4 × 8 MATERIAL (m² × plate) Total (m²) 21 21 21 67 11 11 11 11 11 6

TABLE 6 Day 1st 2nd 3rd 4th 5th 8th 9th 10th 11th 12th Day of week Mon Tue Wed Thu Fri Mon Tue Wed Thu Fri Concentration of 500 ppm 500 ppm 500 ppm 500 ppm 500 ppm 500 ppm 500 ppm 2000 ppm 2000 ppm 2000 ppm ambient carbon dioxide gas

TABLE 7 Name of Screening Screening A AM Screening (400 lpi) Screening B FM Screening (Staccato 20, produced by CREO Inc.) Screening C FM Screening (Randot X20, produced by Dainippon Screen Mfg. Co., Ltd.) Screening D FM Screening (Fairdot, produced by Dainippon Screen Mfg. Co., Ltd.) Screening E AM Screening (175 lpi)

TABLE 8 Change in 50% Gradation Density (assuming that the density at the start on the 1st day is ±0.0%) Day 1st 2nd 3rd 4th 5th 8th 9th 10th 11th 12th Day of week Mon Tue Wed Thu Fri Mon Tue Wed Thu Fri Example 1 ±0.0% −0.25% −0.50%  ±0.0% −0.50% −0.25% +0.25% +0.50% −0.25%  ±0.0% Example 2 ±0.0% +0.25% +0.25%  ±0.0% +0.50% −0.50%  ±0.0% −0.75% +0.50%  ±0.0% Example 3 ±0.0%  ±0.0%  ±0.0% +0.75% +0.25%  ±0.0%  ±0.0% −0.25% −0.75% −0.75% Example 4 ±0.0%  ±0.0% +0.25% +0.25% +0.25%  ±0.0%  ±0.0% +0.25% +0.25% +0.50% Example 5 ±0.0% −0.50% −0.50% −0.25% −0.25% +0.25%  ±0.0% −0.50% −0.25% −0.25% Example 6 ±0.0% −0.50% −0.50%  ±0.0% −0.50% −0.25% +0.50% +0.25% −0.25% −0.25% Example 7 ±0.0% +0.75% +0.75%  ±0.0% +0.50% −0.50% +0.25% −0.75%  ±0.0%  ±0.0% Example 8 ±0.0% +0.25%  ±0.0% +0.25% +0.25% +0.50%  ±0.0% −0.25% −0.25% −0.25% Example 9 ±0.0%  ±0.0% +0.50% +0.75% +0.50%  ±0.0% −0.25% −0.25% +0.25% +0.25% Example 10 ±0.0% −0.75% −0.25% −0.50% −0.50%  ±0.0% −0.25% −0.25% −0.75% −0.50% Comparative Example 1 ±0.0% −0.25%  ±0.0%  ±0.0% +0.25% +1.00% +1.75% +2.75% +3.25% +3.75% Comparative Example 2 ±0.0%  ±0.0% +0.25% +0.50% −0.25% +1.25% +1.25% +2.00% +2.75% +3.75% Comparative Example 3 ±0.0% +0.25% +0.75%  ±0.0% +0.25% −1.75% −1.50% −0.25% +1.25% +2.25% Comparative Example 4 ±0.0% +0.25% +0.25%  ±0.0% +0.25% −0.50% −1.50% −0.25% +1.00% +2.00% Comparative Example 5 ±0.0%  ±0.0% +0.25% +0.25% +0.25% −0.75% −1.25% −0.75% +1.25% +2.25% Comparative Example 6 ±0.0% −0.25%  ±0.0%  ±0.0% +0.50% +1.00% +1.75% +2.50% +3.75% +4.50% Comparative Example 7 ±0.0% −0.25% +0.50% +0.25%  ±0.0% +1.00% +1.50% +2.50% +3.25% +4.25% Comparative Example 8 ±0.0% +0.50% +0.25%  ±0.0% +0.25% −1.25% −1.25% −0.25% +2.00% +2.75% Comparative Example 9 ±0.0%  ±0.0% +0.50% +0.25% +0.50% −0.50% −1.50% −0.75% +1.25% +2.75% Comparative Example 10 ±0.0% +0.25% +0.50%  ±0.0%  ±0.0% −0.25% −1.50% −0.75% +1.00% +2.75% Comparative Example 11 ±0.0%  ±0.0% +0.25% −1.50% −1.00% −1.00% −1.00%  ±0.0% +1.25% +1.25% Comparative Example 12 ±0.0% −0.25% +0.25% −1.50% −1.75% −1.25% −1.00%  ±0.0% +1.25% +1.25% Comparative Example 13 ±0.0% −0.50% −0.50% −1.00% −1.25% −1.50% −1.00% −0.25% +0.75% +1.50% Comparative Example 14 ±0.0% −0.25% +0.50% −1.25% −1.75% −1.00% −1.00% −0.25% +0.50% +2.00% Comparative Example 15 ±0.0%  ±0.0% +0.50% −1.50% −1.75% −1.00% −1.50% −0.25% +0.50% +1.75% Comparative Example 16 ±0.0% +0.25%  ±0.0% −1.25% −1.00% −1.50% −1.25%  ±0.0% +1.25% +1.25% Comparative Example 17 ±0.0%  ±0.0% +0.25% −1.50% −1.25% −1.50% −1.50% +0.50% +1.00% +1.50% Comparative Example 18 ±0.0% −0.50% −0.25% −1.75% −1.50% −1.00% −0.75% −0.25% +0.50% +2.00% Comparative Example 19 ±0.0% −0.50% +0.75% −1.25% −1.75% −1.25% −1.50% −0.25% +0.50% +2.00% Comparative Example 20 ±0.0% −0.50% +0.25% −1.50% −1.50% −1.50% −1.00% −0.25% +1.00% +1.75%

The electric conductivity-based replenishment system for Comparative Examples 11 to 20 was effected according to the method described in JP-A-64-21451 (corresponding to U.S. Pat. No. 4,882,246).

As can be seen in the aforementioned results of evaluation, Examples 1 to 10, which employed the inventive system, showed a change in 50% gradation density falling within the tolerable range while Comparative Examples 1 to 20 showed a change in 50% gradation density deviating from the range of from −1.0% to +1.0%.

In accordance with the invention, even when the electric conductivity sensor of the automatic developing machine is out of order, the automatic developing machine can be temporarily operated on an area and time lapse-based replenishment system, eliminating the necessity of fully suspending the operation of the apparatus and hence minimize the drop of the processable amount of the plate material. As a result, the cost of production can be reduced.

During the development of a large number of sheets of exposed photosensitive lithographic printing plate precursor with a developer comprising an aqueous solution containing an electrolyte, a measured value of electric conductivity of the developer is used to determine the amounts of the time lapse replenisher/processing replenisher optimum for ambient conditions/processing conditions of each occasion. Replenishment is effected according to the time lapse replenishment rate/processing replenishment rate thus determined to keep the sensitivity of the developer stable. In this manner, despite the simple and inexpensive device configuration, the change of reference electric conductivity with the fluctuation of frequency of processing (ratio of processing replenishment rate to time lapse replenishment rate) can be corrected. Further, even when the concentration of atmospheric carbon dioxide gas varies or when different kinds of photosensitive materials are processed, the time lapse replenishment rate/processing replenishment rate can be automatically set close to values optimum for these conditions, making it possible to realize an automatic developing machine having a high sensitivity stability. Moreover, even when the electric conductivity sensor is out of order, the replenishment system can be switched to a substitute replenishment system, making it possible to continue the processing of the plate material.

The entire disclosure of each and every foreign patent application from which the benefit of foreign priority has been claimed in the present application is incorporated herein by reference, as if fully set forth. 

1. A development replenisher replenishment method in an automatic developing machine for a photosensitive lithographic printing plate precursor, the method comprising: developing a plurality of sheets of exposed photosensitive lithographic printing plate precursors with a developer containing an electrolyte while replenishing a development replenisher to keep a developer activity constant, wherein an electric conductivity of the developer is measured every constant period; a development replenisher is replenished every constant time as a time lapse replenisher in an amount based on a set value of a time lapse replenishment rate; a development replenisher is replenished every processing of a constant area of a photosensitive lithographic printing plate precursor(s) as a processing replenisher in an amount based on a set value of a processing replenishment rate; a calculated value of an electric conductivity is calculated from an amount of the time lapse replenisher and an amount of the processing replenisher; and when a set value of a replenishment system indicates an electric conductivity system, the set value of the time lapse replenishment rate and the set value of the processing replenishment rate are increased or decreased according to a result of a comparison of the calculated value of the electric conductivity with the measured value of the electric conductivity of the developer, or when a set value of a replenishment system does not indicate an electric conductivity system, the set value of the time lapse replenishment rate and the set value of the processing replenishment rate are not increased or decreased.
 2. A development replenisher replenishment method in an automatic developing machine for a photosensitive lithographic printing plate precursor, the method comprising: developing a plurality of sheets of exposed photosensitive lithographic printing plate precursors with a developer containing an electrolyte while replenishing a development replenisher to keep a developer activity constant, wherein an electric conductivity of the developer is measured every constant period, a set value of a time lapse replenishment rate is integrated to an integrated value of the time lapse replenishment rate every constant time; a set value of a processing replenishment rate is integrated to an integrated value of the processing replenishment rate every processing of a constant area of a photosensitive lithographic printing plate precursor(s); a percent replenisher replacement which is a ratio of a developer replenishment to a developer in a developing tank is calculated; a percent time lapse replenishment which is a ratio of a time lapse replenisher to a developer in a developing tank is calculated; and thereafter, when a sum of the integrated value of the time lapse replenishment rate and the integrated value of the processing replenishment rate exceeds a value of the lowest replenishment amount, and a set value of a replenishment system indicates an electric conductivity system, steps (A-1), (A-2), (A-3), (A-4), (A-5) and (A-6) are executed, or a set value of a replenishment system does not indicate an electric conductivity system, steps (B-1) and (B-2) are executed: (A-1) a time elapsed between the last time of replenishment and a present time is measured, and a first calculated value of an electric conductivity is calculated from the elapsed time and the percent replenisher replacement; (A-2) the set value of the time lapse replenishment rate and the set value of the processing replenishment rate are changed according to a result of a comparison of the first calculated value of the electric conductivity with the measured value of the electric conductivity of the developer; (A-3) a second calculated value of an electric conductivity is calculated by utilizing the percent replenisher replacement and the percent time replenishment; (A-4) the set value of the time lapse replenishment rate and the set value of the processing replenishment rate are changed according to a result of a comparison of the second calculated value of the electric conductivity with the measured value of the electric conductivity of the developer; (A-5) a developer in a developing tank is replenished with a replenisher in an amount corresponding to a sum of the integrated value of the time lapse replenishment rate and the integrated value of the processing replenishment rate; and (A-6) the integrated value of the time lapse replenishment rate and the integrated value of the processing replenishment rate are initialized, (B-1) a developer in a developing tank is replenished with a replenisher in an amount corresponding to a sum of the integrated value of the time lapse replenishment rate and the integrated value of the processing replenishment rate; and (B-2) the integrated value of the time lapse replenishment rate and the integrated value of the processing replenishment rate are initialized.
 3. The development replenisher replenishment method in an automatic developing machine for a photosensitive lithographic printing plate precursor according to claim 2, wherein a value of the electric conductivity at which the developer activity falls within a proper range is calculated as a target value of the electric conductivity; and when a set value of a replenishment system indicates an electric conductivity system shortly after a starting of an operation of the automatic developing machine, steps (C-1), (C-2), (C-3) and (C-4) are executed, or when a set value of a replenishment system does not indicate an electric conductivity system, a developer is replenished with a developer replenisher according to a period of time during which the operation of the automatic developing machine has been suspended: (C-1) an electric conductivity of the developer is measured every constant period; (C-2) when the measured value of the electric conductivity of the developer is lower than the target value of the electric conductivity, the developer is replenished with a development replenisher in a predetermined amount; (C-3) the target value of the electric conductivity is renewed with the replenishment; and (C-4) the steps (C-1), (C-2) and (C-3) are repeated until the electric conductivity of the developer exceeds the target value of the electric conductivity. 